I've caught bimacs in California. All you need is a fishing license and to make sure you are not in a protected area / reserve. Save yourself days of trial and error and find someone who knows where, when, and how to catch them. The local crabbers are a good bet. Here in California, some recreational fishermen catch octopus for use as bait. If you ask around at a few local bait/tackle shops they might know how to catch them, or at least where. You can also ask a local dive club if they ever see octopus, just to find out if any live there.
The basic method here in CA is to go down to the tidepools at really low tide (less than -0.5 feet) and tip up rocks to see if there's an octopus under it. Don't roll the rocks all the way over, just tip them up on edge, and put them back down in the same place when you've had a look. Otherwise you may kill/squish things growing on the rocks, or destroy habitat. Never flip the rock and leave it upside down, or you'll kill everthing living on it. Big flat rocks are best (but not so big that you risk getting hurt!). And do it in water that is only a few inches deep. That's what works here, but your local species (if you even have one) may have a completely different MO.
Isn't the water sort of cold in NJ? I need a chiller to keep my tank at 62 degrees because the local water is that cold. Will room temp be too warm for a NJ octopus?