why does my dogface puffer swell and swim up side down? What do I need to do?
Sounds like it managed to inhale air (more likely) or has a swimbladder problem. Some have had luck "burping" them by holding them down while inside of a vented container. The pressure can help in "burping" them. The puffer can often (not always, though) burp itself, as well. Sometimes, the issue persists and can dramatically affect feeding habits, etc. to the point of death. Swimbladder issues, however, usually can't be remedied and the fish is often in that state for the rest of its life. Sometimes they learn to eat and function that way, in which case they can live out their lives reasonably normally.
If you need more help, please make another thread so that your situation can be addressed more personally. That way the current thread can stay on topic with the OP.
As for the puffer above, it looks like the classic signs of a fish that has inflated.