If you see threads, it means the nuts have already been removed for you.
It could be that it'll be loose enough to just come right off when you lift up...could be that you'll need to work it back and forth a bit while you lift to get it to start raising up and eventually come off.
Getting it back on...a little more fun.
Might be a good idea to have an extra set of hands available for the first couple of times.
Roll the window down before you start, and dont forget to release the strap at the bottom of the door before you start.
Its all good after you get the hang of it.