Click the "Start" menu button, type "Live" into the search box and click the "Live" icon to launch Ableton Live. Click "Options," then "Preferences."
Click the "Audio" tab, click the drop-down menu next to "Audio Device" and select your sound card from the list. Click "Input Config" and highlight "1 (mono) & 2 (mono)" and "1/2 (stereo)" if they are not already highlighted. Click "OK." Close the "Preferences" window.
Plug in your guitar. If you're using an electric guitar or an acoustic guitar with a pickup, plug it straight into the sound card's "Line In" jack. If you're using an acoustic guitar with no pickup, plug the microphone into the sound card's "Mic" jack and position it so that it will pick up the sound of the guitar.
Click the "S" button in Track 1, which is marked "Audio," to solo it. Click the circular "Record" button underneath the "S" button to arm the track for recording. Click the tempo, which is located in the top left-hand corner next to "TAP" and set the tempo at which you wish to record.
Click the circular "Record" button in the first clip underneath "Audio" to start recording. Play the chords you want to loop on the guitar. Click the "Stop" button at the top of the window when you're finished.
Click "Loop" at the bottom of the window to highlight it, if it's not already highlighted. Drag the warp markers at the top of the recorded waveform to the beginning and end of the portion of the audio you want to loop. Click the "Play" button inside the recorded audio clip to play the guitar loop.