FOR WINDOWS 10
This video shows a simple setup to interface the Ultra PicoKeyer to your computer sound card. The headphone jack output of the Ultra PicoKeyer is used and a stereo audio cable runs from there over to the MIC INPUT or LINE INPUT of your soundcard. Also, a simple free software DSP BANDPASS FILTER is used to filter out virtual all of the harsh square wave harmonics of the original sidetone audio output of the Ultra PicoKeyer.
Note: though this example shows a setup using LINUX, the same concept will apply to a WINDOWS or MAC computer. The only difference will be in which free software audio bandpass filter plugin you decide to use. For windows here is one option as a VST PLUGIN: http://www.meldaproduction.com/MBandPass
Note: turn OFF MIC BOOST,(if you are using MIC INPUT) and you also need to make sure you turn down almost all the way your sound card recording volume for either the MIC INPUT or the LINE INPUT so that the output of the Ultra PicoKeyer volume does not overwhelm your sound card input causing distortion. (On this video I have lowered the volume slider for the computer's MIC INPUT all the way down.)