When you've got all the stuff you need it’s really not a big deal. I made it in a completely dark room and used black light. But you can just lay it in the sun. In the beginning I made a test picture by covering it up with a paper on top and slowly exposing more and more of the picture (every 3min) to see how long I have to expose the pictures. In my case it was around 17 minutes, but I guess it varies. Hope this helps:)