First thing you need to do is to figure out for sure if you need to tie your pipe in before or after that regulator. I know you said the new stuff has it's own regulators, but that in itself doesn't mean anything.
I don't do a lot of work with propane, but many times you need a main regulator (like you appear to have there), and then another smaller regulator at each appliance.
Either way, it looks easy to do. The fitting on the copper looks like a standard flare nut with an adapter that goes to 3/4" male pipe threads into the regulator.
If connecting your pipe before the regulator loosen the flare nut, remove the adapter, install a steel 3/4" tee with a nipple into the regulator and put the adapter and flare connection back into the bottom of the tee. Test with soap to make sure there aren't any leaks.
If connecting your new pipe after the regulator loosen the flare nut and disconnect the copper, spin the regulator off of the steel pipe, install a steel tee with nipple onto the steel pipe, spin the regulator back on and reconnect the flare nut with copper. Test with soap.
You don't need any special dialectric fittings between copper and steel gas piping, if that's what you were asking. You just need a way to go from copper to pipe threads, which usually means using flare fittings or standard solder-type fittings with high temperature brazing alloy instead of soft solder.
Also, copper gas pipe is the same as copper water pipe. At least it is where I live. As long as it is at least "Type L" it should be OK. Soft copper is sometimes sold by it's O.D. dimensions instead of it's I.D. dimensions like hard copper usually is, which creates confusion, but it's the same pipe and can be used for either purpose.
Some areas of the country might require "Type K" copper for gas, (which is thicker), but you don't need to know this for the job you're doing. Just deal with the steel pipe threads that are already there and you should be good.
