Jumping up and down isn't jump roping in boxing terms, you have to mix it up with weight shifts, crossovers, leg crossing, two rotations on one jump, running in place, and on and on. Kinda like your dancing. I can't really explain to you how to jump rope through typing, you have to see it.
If your at a gym, I'm sure there's some dudes in there that will be willing to show you.
Here I found some vids
This guy is a little clumsy, but is what good beneficial jump roping should look like
YouTube - Jump Rope Training - RossTraining.com
This guy shows you what a beginner should look like, although he is the most retarded unskilled "certified boxing trainer" I've ever seen lol.
YouTube - Boxing Training Tips: Free Online Lessons for Beginners : Jump Rope Training for Boxing: Free Online Lessons
These are just some stupid little examples so don't take em seriously, you'll eventually get your own little rhythm going.