Mic preamp out (mono), to computer in (stereo)

I’m wanting to get my vocals in mono on one track but going out of my ART Tube MP into my computer sound card is from a 1/4" out jack (mono, I think?) to a 1/8" stereo in jack to my soundcard. What’s the easiest way to go from a microphone’s mono output to the stereo in? Which cable from the Shack would I need? Or, is there a way to do a setting in Audacity to make the track mono? (I did a test last night and the mic could only be heard on one side.)

OK, well, that’s a start:


Followed by:


Remember you need to go into the Line-In of your deskside machine sound card. This MicPre puts out enough level to blow Mic-In electronics across the lawn and out to the mailbox on the corner.