Go to the body page. You can do it from the dashboard: or by going to Bodies menu and searching it there.
You will see the table like this: If you don't see the "View payments" or "Add payment" columns, that means that either you don't have the permissions to view/set fee payments for the members, or the body is set in a way that it doesn't pay fees (European bodies for example).
To view fee payments for a member, press "View or manage payments":
The modal with list of fee payments will open:
To add a fee payment, press "Add fee payment:
The modal will open:
Fill in all of the fields (the ones required are marked with a red asterisk) and press "Add fee payment". Please check everything twice before.
If you filled in some fields wrong, the red notification will appear and the fields that were wrong would have the red text under them:
If everything was okay, the green notification will appear and the window will close.