The best way is to set up the hammock at home and do a few test runs. Rigging a standard bag can be tricky, and its best to fine tune the system under friendlier conditions.
Shockcord works best to allow the bag/uq to flex and move as your body loads the hammock. Some have used binder clips to attach the cord to the bag. Some sew on grosgrain or webbing loops (I know, that'd be permanent, but done discreetly it won't be that noticeable and its a secure tie off point).
You can also cinch a small pebble or object in the fabric of the bag and then tie (larkshead) the suspension to that bundle. The object gives you something secure for the rope/shockcord to grab.
Tie off to the four corners of the bag (I did a quick search and dont see a BA Copper Creek bag...so I cant say which bag you have, BA has a copper spur bag or a gold creek? Both are mummy style).
Suspend the bag, and adjust acordingly as needed. Tweaking the ends so you get a good seal is tough too. If you can not get a snug closure at the head and foot ends, it wont matter what you hang under you...the heat will escape and you'll be cold.
Maybe pick up a closed cell foam pad or inflatable pad for this impromptu trip.
Again, its best to get your system right at home. Then it wont be a bad night in the woods.