Audacity is a great free tool for recording your mixes. For connecting it to your pc, use a cable that connects to your mixer/controller output and goes in to your line in on your PC. If you open up audacity you can see a recording device. You should select that and then select your audio input. To hear your mix you can either use your mixer/controllers booth monitor output or go windows sound options and select recording devices. Double click your line in and select: listen to this device. That way you can hear your mix while recording. Be aware that publishing music/mixes you do not own the rights to is illegal.