If you are talking about the background that has its own adhesive, it is done with soapy water, a credit card and lots of patience. That is the kind I used and you basically follow the instructions that come with it.
1. Measure and cut to fit.
2. CLean the aquarium glass really well and use a lint free cloth if available. Any bit of lint show up, at least on the black backgrounds I use.
3. Remove protective film from paper.
4. Apply mildly soapy water to background and glass on tank.
5. Using a credit card slowly flatten it out starting in the middle and working your way out.(this takes time and patience)
Sorry, can't offer much with that. That is why I bought the self adhesive. I did not like the loose background with scotch tape and I had no idea how to attach it either so it would looked nice.
I do highly recommend the self adhesive stuff though. It is made by Oceanvisions.
I have a non-adhesive background. I didn't like having tape wrapping around the sides, and it's impossible to get it to lie flat to the glass by taping along the top and bottom since the frame sticks out, so I got some double-sided cellophane tape to stick it on, and I'm reasonably pleased with it.
I've never seen the adhesive stuff. I'll have to look into that.
ADDED LATER:
I just did some research - it seems that Oceanvisions only comes in solid colors. I like my sand, plant and driftwood background.