You add a player to a Tennis for Kids course manually from the course attendees page by selecting 'Add participant'.
You'll need to add details for the parent/guardian and the junior player.
After adding the player you will need to send a payment request to the player so they can fill in their kit requirements and pay for the course. The payment request will be sent to the player's main contact.
Payment requests can also be sent from the course attendees page (click on reference name next to Tennis for Kids at the top of the page to return to this) by selecting the tick box next to the player's name, followed by the '£' icon above the table.