Once a schedule is published, you can still make changes to it if needed. If they are significant changes that affect a large number of games, you can unpublish your schedule right in the schedule builder tool, make your changes, and re-publish.
If it is just minor changes, it is recommended to make the changes from the Scheduling tab instead of the Schedule Builder.
Once you make a change, it also changes the team management app for all the teams affected, as well as your league website.