There are a ton of videos on youtube, too.
To get your placement correct on two different towels, here's how I do it..there are dozens of ways, though. I would measure from side to side and top to bottom, and mark (chalk) my placement spots. On my hoop I have raised arrows marking the center of all 4 sides. Once you have the area squared and marked on your towel, then just use you marks on hoop to line it up.