After you have started a tournament (see article on how start the tournament – LINK), your students will be able to join the tournament. Once you click ‘Start Tournament’, students will see a pop-up on their screens which will say that the tournament has started and they can join, as shown below:
And when they click on “Join”, they will be enrolled to the tournament.
Late-Join
Your students can also join a tournament late if they have missed the first few rounds. You can find more details about late-joiners and exiting tournaments here – LINK