While creating your event (league), you are asked if you want to use the League Fee Payment feature. If you said no at the time but changed your mind, you can turn it on by going to:
Menu > Manage > Event > Event.
Select your current league;
Pencil to edit;
Click on the Weekly Fees/League Fees Payments section;
Accept League Fees (Weekly Fees) Payments? Check the box.

When you check the box, the system will ask you if you accept the charges that come with using this feature.

If you agree, say yes.
It will then ask you if you want to accept online payments.
Leave blank for no, this will give you the tools to keep track of the money coming in, (cash, transfers)
Check the box, if you want players to be able to pay directly on CompuSport.
It will ask you if you want to Hide Teams Stats for teams that have unpaid matches.
Click to connect a Stripe or Square account.
So have access to the Connect to Square, you need to be on CompuSport.us.
Once you are done going through the steps
What is the cost to use the League Fee Feature (Weekly fees/Online Payments)