According to USA Today, players have to be cleared before travelling to Orlando and are then tested immediately upon arrival at Disney. They can't leave their hotel room until they've completed two negative COVID-19 tests (though Bucks player and mega-Disney fan Robin Lopez didn't seem to mind much). If you're curious, the Sixers' Matisse Thybulle documented his time in quarantine on his YouTube channel.
Once they've passed quarantine, they must complete daily tests to stay on campus. Two players have already tested positive while in quarantine, and those players were ushered off campus to isolate at home or in isolation housing until they are cleared to return.