A package is a template of resource limits, disk, bandwidth, databases, email accounts, subdomains; that you apply when creating a hosting account. Get them right and running a reseller business is mostly clicking a dropdown. Get them wrong and you are editing accounts individually forever, or explaining to five clients at once why the disk is full.
The mistake almost everyone makes is designing packages around what sounds generous rather than against the allocation they actually have. This covers the arithmetic first, then the fields, then the changes you will want later.
Start from your allocation, not from your price list
Your reseller plan gives you a fixed pool: a number of cPanel accounts, a disk allocation and a bandwidth allocation. Everything you sell comes out of it. An Ahosting R Bronze plan, for example, provides 5 cPanel accounts and 15GB of SSD disk.
So the sum of what you promise has to relate to what you hold. Five accounts at 10GB each out of a 15GB pool is 50GB promised against 15GB owned. It works perfectly until clients start using the space, and then it fails for everyone simultaneously.
Overselling is a legitimate business model: most hosts do it, because most accounts use a fraction of their quota. But it is a decision to make deliberately, with a ratio you chose and a plan for what happens when usage rises. It is not something to arrive at by accident because 10GB sounded like a good number.
The conservative approach, and the right one when starting: size packages so that if every client filled their quota you would still fit. Then you can promise what you actually have.
Creating a package
In WHM, open Packages then Add a Package.
Package name. Visible to you, not to clients. Use something that says what it is, starter-3gb beats package1 when you have nine of them.
Disk quota. In megabytes. The main number to size against your pool.
Monthly bandwidth. Same reasoning. Unlimited is available and means "unlimited within your own allocation", which is worth understanding before you print it on a price list.
Max FTP accounts, email accounts, mailing lists, databases, subdomains, parked and addon domains. These cost you almost no disk individually, but they define what the client can do. Being too tight here generates support requests; being unlimited on addon domains means one account can host forty sites on a plan you priced for one.
Addon domains is the field to think hardest about. It is the difference between selling one site of hosting and selling a small reseller account by accident.
Dedicated IP. Leave off by default. Ahosting reseller plans include one free dedicated IP; that is a resource to assign deliberately, not something to bake into a package that every client receives.
Shell access. Leave off unless a client has a specific need and you trust them.
How many packages
Three is usually right: a small one, a normal one, and a larger one. Clients understand three options, and each maps to a price.
Nine packages feels thorough and produces a support burden, because every one is a slightly different set of limits you have to remember. If two packages differ only in a field nobody asked about, merge them.
Add a private package for exceptions rather than reshaping a public one. There is always a client who needs one unusual thing.
Changing a package later
Editing a package changes the template. Existing accounts already created from it do not automatically change, and that catches people out.
To apply a changed package to existing accounts, use Upgrade/Downgrade an Account and reapply the package to each. WHM does not do it in bulk for you, which is another argument for having few packages rather than many.
To change one account without touching the package, modify the account directly. Editing cPanel account resources goes into it. Use it for one-off exceptions, not as a habit; an account whose limits no longer match any package is a small mystery for whoever looks at it next, including you in six months.
Deleting a package does not delete accounts created from it. Those accounts keep their limits and simply stop being associated with a package. It is tidy enough, but check nothing depends on the name first, billing software often references packages by name, and removing one can break provisioning silently.
Naming that survives contact with a price list
Package names show up in WHM, in your billing software, and in your own notes. Make them describe the resources instead of the marketing.
A package called gold tells you nothing when you are trying to remember whether it was the 5GB or the 20GB one. A package called web-5gb-10db tells you immediately. Marketing names belong on the price list, where you can change them without touching anything technical.
Before you sell the first one
Create a test account from each package and look at what a client actually receives. Log into its cPanel from WHM's List Accounts screen, no password needed, and check the quota display shows what you intended.
This catches the most common package error, which is a disk quota entered in the wrong unit. A package intended as 5GB and entered as 5MB looks fine in the package list and fails the moment a client uploads anything.
With packages defined and tested, you are ready to create accounts. Adding new client accounts deals with doing that one at a time and in bulk.
For changing one later, and what that does to existing accounts, How to Edit or Remove Hosting Packages walks through it.
What goes in each package, and what it should cost, is the commercial half. How to Price and Package Reseller Hosting Plans goes into it.