Hi! How can I delete someone from our club who hasn't been playing for a very long time?

If you are a president or officer you can remove members by pulling up the member list and tapping on the red button next to the member's name. If the player is an officer, then the president must demote them first.

Once the spot is vacant it can be filled by a new player. If the club is an "open" club, the new player can "join" and be included. If the club is an "application" club, then the new player can "apply" then await president/officer to admit them to the club.