There are a bunch of different clubs on island. My best advice would be to go on Facebook and look up the Oahu Golfing Group. There are tons of folks who get together and go out.
Most club play is usually once a month at a rotating group of courses on the west side. If you’ve played anytime in a Saturday at Hawaii Prince, Royal Kunia, etc you’ll see folks in matching shirts.
Hawaii is still low tech in that we rely on Facebook but it’s a good way to connect. I’ve been able to play a few private courses I wouldn’t be able to get on via this method.