What's been said above is right, but I'll add a couple things.
I'd buy a new threaded fitting rather than trying to desolder and reuse it, or trying to install two couplings and a piece of new pipe.
If you don't care if the hose bib/spigot is higher, just cut the pipe and solder a new threaded end on (or get a hose bib that solders on directly). If you want the hose bib in the current spot (or lower), now's the time to go buy some additional copper pipe and add it with a coupler.
Before cutting the old pipe with the tubing cutter, sand it with the emory cloth or 120 grit sandpaper. It's a lot easier to get a nice clean sanding job on the pipe before you cut it. Then, fit the coupler, new length of pipe, new hose bib assembly. If you want to assemble the new pipe and hose bib on the bench, you can. Then you only need to assemble the final coupler to the house in the vertical position. Apply flux to the cleaned fitting (solder both sides at once), assemble it all, and you can push the assembly together with a piece of scrap lumber or something to hold everything tight while you solder it up. Open the hose bib (this will let the steam that you'll boil out of the pipe and the flux vapors have a place to go rather than pushing the solder out of the joint to escape). Heat the coupler and the pipe, moving the flame around a bit (1/2" is small enough that this isn't super critical). Don't use the flame to melt the solder. Use the flame to heat the coupler and melt the flux hot enough to melt the solder when it touches the joint.
If you don't give the steam and flux gases a place to go, you'll have a hell of time getting the solder to stay in the joint and make a good seal. If you do, it's easy once you've done a handful of joints. It's hard to make things too clean. Clean it well, use a nice even (but not crazy thick) coating of flux, and a torch with good heat. Wipe the joint with a wet rag while it's still pretty hot, then let everything cool and don't burn yourself.
Big box stores sell a black soldering flame protector, lead-free solder, flux, brushes, and emory cloth. Use lead-free solder (leaded solder is slightly easier to use, but can't be used for drinking water pipes and I don't like having it around and having to keep track of which parts are lead-free and which aren't).
Watch a few videos as suggested earlier.