Can't get sounds in-line with mic to Audacity on WinXP

Done a couple of test recordings using a Presonus AudioBox USB to run a Shure SM58 into Audactity 2.1.1 on an old WinXP box. Comes in on the 'mic' input jack. Works fine.

Wanted to add some in-line sounds, (applause, explosion, horn) to underline various comments as I recorded, rather than try to lay them in after. Chose your EXP SoundBoard for good reviews and most recently worked on.
Can get Audacity to record the Soundboard clips or the Presonus or mic inputs (seem to be the same), but not both. Just change the Mic input there between VB-Audio Point (your sounds) or Primary Sound or Presonus AudioBox (microphone).
Using the VB-cable s/w, followed the settings that it specifried, followed the settings yours specified. No dice.
Spent a couple hours banging on this, walking through different settings, never got any better.
Thought I'd write, see if you (or anyone) had developed any more extensive documentation.

Maybe buying a hardware mixer, and dedicating this PC to just playing sounds, would work. Probably easier. May try on the Win7 and Win10 boxes. But the old one I could dedicate to the recordings set-up. The other two actually have to travel.

Looks like a nice app.