Download audio recording software for your PC or laptop. Many free options are available, including Audacity, RecordPad and Audio Record Wizard (See Resources). Choose the program you want and download it. Install the program on your computer. Set the program to record from "Line in."
Locate the "Line in" jack on your PC. Look for the ports that come from your sound card (generally where you connect speakers or other audio devices) and find the 3.5mm jack. Standard color code for sound cards indicates that this jack should be light blue. Connect the 3.5mm end of your converter to this jack. Connect the guitar cable side to the "Output" jack on the back of the RC-20XL. This is located to the left of the "DC In" jack.
Choose the desired phrase using the "Phrase Select" dial in the center of the RC-20XL. Select the phrase you want to record. If you want to combine multiple phrases to form a song, you can do this using either the looper pedal's "One Shot Playback" function or audio editing software.
Adjust the "Level" dial on the RC-20XL. Check your audio editing software's meters to see what the appropriate level is. Ideally, the loudest parts in the music should move the meters into the red. Test the phrase by pressing the left pedal to start playback. Stop playback by pressing the right pedal.
Select "One Shot Playback" mode if you only want each phrase to play through once. Press and hold the "Shift" button, which you can find by looking under the "Phrase Select" dial, then press "Loop/One Shot." The "Loop/One Shot" button is located to the right of the "Shift" button. The "One Shot Phrase" light beside the "Phrase Select" dial will light up when "One Shot Playback" is activated.
Set your audio recording program to record, then play the phrase you want to record on the RC-20XL.