If you look at that link, there is actually a video you can watch that shows you some stuff. You can spray over them, ink over them, paint, use chalks, etc.
If you google "Crafter's Workshop" and go to their official website, they have a section with video tutorials that will give you even more ideas.
I usually use spray inks with them. I use re-positional or removable adhesive to hold it down and then spray. On the more basic templates you could also trace them and even stitch over the traced lines.