Tracktion 5 / Focusrite Sapphire

[Mikehicks01]

Hi all, newbie here.

I'm using Tracktion 5 with a focusrite sapphire interface and I'd like to record the audio from the pc, for example a YouTube video. Can this be done internally or does the audio output have to be routed back into a physical input on the interface? I have a small 4 track mixer that could work.

I've tried everything to get the pc audio to show in the inputs assigned to separate tracks.

TIA for any help offered.