2
Leave the wound open.Don't put a dressing on it or cover it. It needs to let air in and out.
3
Bleeding around it: if needed, press directly on the bleeding to control it.
4
If you're trained and have one, you can use a special vented chest dressing that lets air out when they breathe out. Keep an eye on it in case blood blocks it.
Older first aid courses taught sealing a chest wound with a dressing. Current guidance is to leave it open.