How to upgrade beta version?

Open up Impulse.  On the top bar there should be a tab called Updates.  Go there, and update as necessary.  Also, right clicking the game in the your games list inside Impulse should give you the option as well.

Initially there wan't any update tab, but I found a "check for updates" option that created the Updates tab.

Thanks for the help!

I assume I am now on .23 but how can I tell?

When you start the game, on the bottom left you can see the version (in the screeen where you can choose to start a skirmish, load/save, etc.)

If you have the Impulse tray app running, it's supposed to tell you when there are updates, but the option to do it for beta software seems to be off by default. Right click on it, go to settings, and enable that.

Next time there's an update, it should tell you.