The simplest way to do this is to go to our invite form and fill it out for the game and player you have in mind. They'll get an email with a link to your game, where they can sign up and pay for a spot.
You can also go to your dashboard and click on the game you want. Now you're on the game page and you can copy the URL from the address bar and give that out to your intended players.
If you're looking to add someone to your lineup for the rest of the season, you can go Behind the scenes and click on Manage Lineup. From there, you can invite new players to whatever rounds you choose.