Tub faucet, how to attach elbow to cut pipe (partially cut threading)?
You should remove that piece you cut (hanging down) with a pipe wrench. Be sure to hold the piping going up to the shower so you don't break anything else loose or in half. Then you can take two pre-threaded brass pipes and a brass elbow (use thread paste) to create the "L" for your tub spout. You can buy those parts at most building supply stores. The straight pipes come pre-cut and threaded and are in several different lengths to suit your needs.