Fly fishing in Hawaii

I have a couple of questions about fly fishing in Hawaii. I’m at Oahu right now but I don’t have fly fishing gear on me as all my gear is back in Alaska, but I would like to try in the future when I come back. I saw a post on here and a guy was fishing in Maui but can you fly fish anywhere where there’s not a lot of people? DIY of course. I wouldn’t mind bringing my fly gear like a rod and some tackle but I wouldn’t know where to go. I’ve only been to Maui and Oahu but it seems fun seeing that one guys post. If I’m not mistaken, there is some salt water bass that can be caught on a fly rod (forgot which island) but I understand wildlife here is super protected for good reasons. I usually bend the barbs off my hooks, but would I get in trouble? I know I got to get a temp fishing license and what not but would really like to learn what’s acceptable and what’s not acceptable. Any insight/tips would be useful in the future. Thanks.