Put 1 to 11/2 cups water into the Instant Pot. Set steamer trivet inside, and arrange the beets on top. Lock the lid in place; turn the pressure release valve to seal. Program the IP to cook on Manual, at High Pressure, for 15 minutes.
Turn off the IP, and wait 8 to 10 minutes to partially depressurize. Release remaining pressure, remove lid, and then transfer the trivet and beets to a plate. When beets are cool enough to handle (about 10 minutes), rub off the skins and trim ugly/hard parts. Halve then quarter each beet (or cut each into 6 wedges). Put in a bowl, and toss with vinegar, oil, and salt. Cool completely before eating, or chill for up to 5 days. Return to room temperature to use.