To add players to a roster, click the grey "Add team members" button at the top of the list of your active players.
If you do not have access to your players test scores, no worries! The athlete will be able to upload that information as a part of their Athlete profile.
To remove players from your roster, click the grey (Remove) button to the right of their name. This will not delete or remove the player's Athlete account, but it will remove the link to your roster.