First, make sure you are logged into your WHM admin side.
1. Scroll down on the left hand side of WHM to packages.
2. Click Add Packages
3. Enter a name for your package, could be "small" for example.
4. In the next fields, enter what you think is appropriate for the package limitations.
5. The dedicated IP option if you wish to have all accounts created with this package to have a dedicated IP. For an example this would be used for SSL.
6. Feature list and cPanel theme can be left default.
7. You are done!