To edit Membership Fees, we'll go to MEMBERSHIPS > Select Membership:

Next, we'll go to the desired membership(s) and press the PENCIL, EDIT icon:

If we go under the select membership and then the MEMBERSHIP PRICE tab:

Check 'Requires Fees' box:

Here you can customize whatever fees you need. Let's say we want to update the 'Monthly' fee of $75 to $90:

Now, check 'Update Existing Memberships'.

Once this is updated, we can see the new price reflected of $90: