Plug your iPad into the new computer using the USB cable that came with your iPad. If iTunes does not launch on it's own, start up iTunes. Make sure you have the most recent version of iTunes.
Here's the part that is counter-intuitive to me. I had to do just this last week. Once you plug in the iPad, it will give you two options: to use as a new iPad or restore from backup. I didn't want to do either, so initially I was confused. Ultimately, I clicked on "new iPad," fearing it would delete everything on my iPad, but it didn't. It just synced my iPad with the new computer.
If you are having other problems, could you please be specific in explaining what you have already tried and where the process seems to get stuck?