Now, you can start to fold on the dotted line. Warm up a line where you want to fold and now you can fold. This step needs time and patience. Don't just try to fold the tab all the way in the first warming session. Keep warming when needed. See the image for clarification on folding. If a tab breaks off, don't worry, just use super glue!
If there are any rough or pointy spots, just use sand paper.