Connect your audio interface to the computer. The audio interface converts the audio signal from your guitar into data that is interpreted by the recording software or digital audio workstation. The method of connection varies according to the make and model of the interface, but typically calls for either a USB or Firewire cable. Connect the cable to the audio interface's output port and to the relevant USB or Firewire port on the computer. Audio interfaces are typically phantom-powered, meaning they draw current from the computer via the connected cable.
Turn the "Master" and "Monitor" dials down on the interface. This prevents any unexpected sounds from being amplified.
Plug your guitar into the relevant socket on the audio interface. Connect a 1/4-inch jack instrument cable to the output jack on your guitar. Connect the other end to the front of the audio interface.
Open your preferred software program or digital audio interface, such as Logic, Pro Tools, Mixcraft or Audacity.
Click "File" and select "Open New." This opens a blank recording session. If you'd prefer to use a work in progress, click "File" and select "Open Recent."
Click "File" and select "New Audio." Selecting "New Audio" audio configures the recording interface to assign the audio interface as the main input device. It will search for the audio interface when in record mode.
Audition the audio interface. Play the guitar as loud as possible. No sound will come out because the volume is down, but the volume meter on the front of the interface will flash to tell you what input level it is receiving. If the volume meter flashes green, it is fine. If it flashes red, this is a sign of signal overload. This manifests itself as distortion on the recording. Reduce the "Gain" dial on the interface to mitigate this. Aim for an input setting that is as loud as possible without creating distortion.
Gradually increase "Monitor" and "Master" volume dials so you can hear the sound of the guitar as it will record. Because the guitar is directly ported, you can play along to a backing track without the backing track "spilling" onto the recording, something that you couldn't do if recording with a microphone.