I agree with mal's opinion...so...how to wear legwarmers? Don't...
No, if you want to wear them, they definitely go over the jeans. But as others have said they have to be TIGHT jeans. /me remembers her tight jeans from the 80s where her mom had to pull them off...ugh
Anyway, they may look cute with a funky skirt and some bright colored tights. Hey, if you're going to wear legwarmers at least look like you're having fun! I'd go for the punk thing...funky plaid skirt, bright colored tights, clunky mary-janes, and a tattered top with plastic bracelets up the arm. Oooo, dressing up is fun!