On your team main page is a prominent table showing what events your team is registered for, and the the status of that registration:

When your team has been Accepted for league play (green rectangle below), you can click on the roster link (red oval below) for that event, and complete the rostering of your team.

You can add players from that page, or update existing player information such as uploading a current picture for the player pass. There are several mandatory fields on that player page. Some of those fields, like address and email, might best be filled in with valid but bogus information. When adding new players, do not enter anything for "Player ID Number" as that is auto-generated when you freeze the roster.

Next, you'll Freeze the roster and print that plus the player and coach passes. Freezing to roster also generates Player IDs, and Coach IDs for the new season.