I have this pump:
https://www.axiomgear.com/products/ge...eair-pro-road/

And you can use it for presta valves, but I don't know how. I've never pumped a presta valve before (it works on my shrader just fine).

I got the cap off (derp) and I unlocked that other tiny nut too, but I can't get the pump to fit the valve. I have managed to completely deflate my tire, with no idea what to do. I don't have an adapter and of course I decided to try this when all the bike stores are closed.

I really want to take this bike to work tomorrow, help?! The web site says this pump has a "reversible head" but I can't figure that out. Anyone own this pump?

To make it a Presta pump -- I dunno, I usually carry a little brass adapter -- Probably unscrew the tip of the chuck and flip the piece inside around 180 degrees ..?

That's how most "reversible-chuck" pumps work. There should be some instructions that came with the pump on how to do that.

See the illustration at:
https://www.axiomgear.com/manuals/enf...r-pro-road.pdf

Inside the head of the pump are two small pieces that need to be reversed to switch the pump to Presta. Unscrew the cap from the head and remove the rubber washer and plastic adapter pieces. Then flip both around and reinstall them. The plastic adapter should go in first and have the little nub pointing into the pump and the rubber washer should have the smaller hole pointing out toward the cap when configured for Presta valves.

This explains it.