Just google the crossover move if you need pictures. While you are skipping after a turn you just cross your elbows which will cause the rope to crossover, you just jump through the loop. It takes a few minutes to learn but once you got it down it'll be fun and to the guys around you'll look like the ish.

The box jump is seperate from skipping, you can google that too or better yet what I was thinking of before is doing a double jump here and there, which is where you jump two turns of the rope.