The best way to add all active athletes to a team would be to export all athletes (Settings-Import/Export-Athletes - Export), Copy the team name in the first column (A), save the file and import it again.
Make sure that team name is matching the one set in team settings (respect case, check for extra spaces, etc), that the ID athlete set for each athlete before exporting the template. Else athlete accounts might be duplicated as the system will try to match users by first and last names.
