To get more members for your MC, other members have to apply for membership with your MC. To apply, they have to visit the profile page of your MC and click on the button “Apply” to send your application.
A little red notification will tell you, if another player has applied for membership to your MC. You then simply open your MC and click on the pencil icon next to the players in the member list to accept or decline membership. Via this pencil you will also be able to change the status of an MC-member after he or she has joined the club.
To get new members, simply write them a personal message and advertise for your club, so that they apply for membership with you or ask others to join in the global chat.