You will have the ability to approve a player/team's entry to participate in the tournament.
Go to the "Tournament Settings".
Go to the "Manage Participants" page.
Use the search bar to search for the player/team. or open go to "Pending" tab and will find all pending users.
Now you can click on the green button to approve the player's/team's participation in the tournament, and the player/team will be automatically moved to the Accepted list.