From Memberships select Registration Fees & Forms.
Select Forms and then Forms made Available to me.
Click Use this Form at the start of the line you wish to select. This opens the form as editable.
Select the Registration Fees and Merchandise tab.
Click Add Existing Registration Fee.
Note:If you can't find the fee you are looking for, use the search bar on the top right.
After adding, if you wish to make the fee mandatory, click the checkbox under Mandatory column.