Since the DCS UH-1 Beta is not yet available on Steam during the writing of this small guide,I'm going to provide you with the few steps you'll need to perform so you can use your legal DCS UH-1 Beta copy within Steam.

Step 1:
Download the full DCS World client from the developers website.

Step 2:
Install the NONE Steam version of DCS World on your computer.

Step 3:
Start the NONE Steam version of DCS World and activate the Huey product with your legal registration key if needed.

Step 4:
Exit the NONE Steam DCS World

Step 5:
Make a copy of your NONE Steam DCS World.

Step 6:
Copy the entire content of the Steam DCS World Software into your copy of the NONE Steam DCS World.

Step 7:
Start your None Steam, Copied DCS World and see if the Huey is still active.

Step 8:
Copy the contents of your NONE Steam, copied DCS World into your Steam DCS World.

If everything went smooth, then you should have a nice Steam version of DCS World with an activated UH-1 Huey Beta.