Once you have it downloaded and installed, open it, it should automatically detect your ArmA 3 install. If it doesn't don't forget to set your ArmA 3 Path, it will prompt you to do this.
Now you're almost ready to go back in time, but before you can do this, select "Mods" from the top navigation bar. Scroll about one quarter the way down, you're looking for "Iron Front (Preview)". Click the "Subscribe" Button to the right. This will then initiate the download from Steam Workshop.
Assuming you've now downloaded the aforementioned. Navigate back to the "Servers" tab if you haven't already. Within the Filters, specifically the "Name:" field, enter "King of the Hill: 1944" then press "Apply". Don't forget you can always join through the Official ArmA 3 Launcher, by enabling "Iron Front in Arma 3 - preview version" only. NOTE: we have been informed that the mod folder name MAY change to @IFA3LITE in the next release.
Manual subscription via Steam can be achieved by navigating to the Steam Workshop item here: Iron Front in Arma 3 - Preview Version.
Now, get in game and kick some old fashioned ass.