My profile shows I am president of a club. How did that happen and how do I remove myself from being..

It could happen if the previous president stepped down and promoted you, or if the previous president did not play the game for 30 days, or if a glitch occurred.

To remove yourself as president, you need to appoint someone to take your place. Tap on your club icon to bring up the club member list. If there are officers, you can promote one of them by tapping the green button next to their name. If there are no other officers, you must promote a member to officer, then promote them again to take your place. Best to discuss with your club, and see who would like to take over.