how to wire circuit directly to battery?

Actually the MOST important thing to be aware of when connecting directly to the battery is to use a fuse, and place that fuse in line as close to the terminal as possible. This is a safety concern. Use the proper gauge wire (which is determined by the total current draw of the circuit, and that will determine fuse size (amp rating).

Now..as far as actually connecting to the battery there are several ways and some depend on the type of terminal that already exists at your positve cable.

If it is a side post you can purchase a side post adaptor at just about any car stereo shop..including the "big boxes". 5 bucks or so should cover that. However unless some mods were done I don't think a Honda will be using side posts.

If the terminal already there connects to a junction (just follow the positve cable until you get to a terminal bolt, you can connect there). On most hondas it is a fairly thick white wire and the junction is at the fuse box under the hood..simply lift the cover and test for constant there.In all these cases you just need to crimp and/or solder a ring terminal of the appropriate size and gauge to the fuse holder. If the vehicle has an aftermarket terminal..usually those have  7/16'' bolts that you can remove one of them and stick the ring terminal there and re tighten the bolt. On a factory terminal you can stick a ring terminal onto the tightening bolt but I don't really like to do that..it works but just don't sit with me as "proper".

If none of the above apply (you did not tell us if the positive terminal is original) you can purchase a cheapo auto parts store replacement terminal and use one of the bolts (there will be 2) or go to a car stereo shop and buy a fancy schmancy gold plated battery post terminal which will have several points to connect different gauge wires to. Those can run upwards of 15 bucks a piece depending where you purchase and the brand.

Now another option since these are just a bunch of LED's and not an amp or other high current device you can go to the constant wire at the ignition harness as well...just make sure you connect your fuse there close to the power source. Try not to get lazy and just shove a wire into a factory fuse..this may work but is not reliable and kinda cheesy and lazy IMO.

Best of luck on your project.