You can invite a player to your club by sharing the link to the club, which is displayed in the club profile in the tab with information about the club. Also, when you open an account of another player who is not a member of any club, you will see an Invite to Club button and send an invitation to that player to be a member of your club. If you want to cancel the invitation, you can press the red Reject Invitation button, which is displayed right after pressing the invite button.