Hi happy,
If you are the owner of the club you need to send invites to those players. When a player requests membership, it's just letting you know that someone is interested in joining your club, however you must still send out the "official club invitation." Once you send the official invite the player will receive a confirmation link at the email they registered with when they first signed up. They will need to click the confirmation link in order to finalize the joining of your club.