Set up a microphone on the speaker of the Spider IV amplifier. Miking an amplifier is a standard studio technique, which you can adapt to the home studio. Close miking gives the best results in rooms without acoustic treatment. If you are recording a combo, isolate the amp and mic in a closet, or place a moving blanket over the amp and mic to reduce sound that may leak into other microphones.
Connect the "PHONES/DIRECT OUT" jack on the back of the Spider IV amp to the input of your recording device using the 1/4 inch TRS patch cable. The format of the other end of this cable depends on your setup. Balanced XLR or a Y-adapter to two 1/4 inch TS phone plugs are preferred. When the "PHONES/DIRECT OUT" jack is connected, the speakers on the Spider IV are muted, so monitoring through headphones is required.
Connect one or two extension speakers to the "SPEAKER OUTS" jacks on the back of the Spider IV. You can mike each separately to take advantage of the Spider IV's stereo effects, or mike a single speaker to capture its own unique sound. If necessary, take precautions to avoid sound leakage from the amp into other microphones, if used.