You can add and edit payments after the payment schedule is published and after parents have signed up.
If you want to add/edit payments for the entire team, go to the team's page. Click 'View Payment Schedule' then click 'Put Payment Schedule in Edit Mode'. 
You can now add, delete, or edit payments for the entire team. Parents who have already signed up will receive email alerts for changed payments. If a payment is added, they will be asked to approve it before they are billed.
If you'd like to edit the payment amount, you can delete the payment item by selecting the trash can icon and re-add it with the updated payment amount.
Note: If the payment item has a yellow icon by it, roll your mouse over it to view the comment. This is usually a note to you to let you know that there are some players who have already made the payment for that item.
After you're finished, you can re-publish the payment schedule. If you do not publish it, the payment schedule will remain "On Hold." This means that any upcoming payments set up with AutoPay will not be automatically charged, and parents will not be able to make payments on their account until the payment schedule is re-published.
If you want to edit payments on a per-player basis, go to the player page. You can edit payment amounts or delete the payment by clicking the dropdown button to the right of each payment in the payment table and selecting the appropriate action. You can also add a payment to only this player by clicking the 'Add Invoice' button.