Before you try to do any cross over, you need to spend a lot of time actually practicing how to do moves on the skates. They aren’t going to be very easy to use and/ or control, which is why you should first learn how to balance and operate on in-line skates.
When you are about to start a cross over, you can try to reduce your speed. Bend your knee and then start to turn slowly. Bring the skate on the outside and move it over the inner skate, once this is done, push with the inner stake and then use your arms to balance yourself and to avoid falling over.
Once the cross over is done bring your skate that was on the outside, in front of the skate that is now on the inside. Once you do this a few times, start doing it over and over again till you get much better at it.
Once you have figured out how to do the cross over, go ahead and start practicing them. Go in the opposite direction and see if that works out for you. After you learn to do it in both directions, go ahead and learn how to start with both feet, so that you can interchange them at will.
The last thing you need to do, is to work on building the pace of the cross over and then you need to practice on how to use your hands to give you balance.