To record and play back audio, Sound Studio needs audio hardware. Most Macs have built-in audio hardware for both recording and playback, but some only have playback capabilities, and some have no built-in capabilities. Check the technical specifications for your specific Mac model.
You may also need other audio equipment such as a tape deck, a record player, a mixing console, or a microphone. You will also need the proper cables to connect the equipment.
Typically, your computer will have a pair of 1/8-inch mini-jacks, one for audio input (recording), and one for audio output (playback). These are usually located near or on the back or side of the computer. Some computers also have a built-in microphone.
To use your audio equipment, set up Sound Studio's Preferences to tell it what hardware to use. Launch Sound Studio, open the Sound Studio menu, and select Preferences. Then select your audio equipment in the dropdown menus for Audio Input and Output.