In your WHM, scroll down the left menu until you get to the "Packages" section.  First you will want to use the Feature Manager to create a feature list - this defines what functionality your users have access to.  After you have done that, use Add Packages to define your disk space, bandwidth, etc.

If you already have some accounts created that aren't assigned to your new packages, you can do so by going to Account Functions --> List Accounts.  There is a column towards the right called Packages.  Click the icon for the account you want to change, and change it.

Good luck.

To my knowledge you cannot customize the reseller features such as space, bandwidth, email account limits, database limits for your reseller accounts. They come pre packaged with the features seen here: http://www.lunarpages.com/reseller-hosting/  that cannot be changed.
Someone correct me if I am mistaken.




Hope this helps,
RandyT