This mod will unlock most units after you finish the tutorial. In addition you will get 6 slots for tanks and 6 slots for artilleries from the beginning. Please note that the tutorial missions are a little more difficult a usual, but you can skip them via the known cheats.
PLEASE CLICK "READ MORE" ON THE DESCRIPTION BELOW FOR INSTALLING THE MOD. This mod will let you play the Rolling Thunder and Burning Horizon campaign with 12 cores units from the beginning (12 armor and 12 artilleries pieces each) + almost all artilleries and tanks upgrades are unlocked respectively for each campaign on the second chapter. NOTE : you still need to play and complete the first three missions of each campaign in order to get the upgrades.
So just to double-check, do I have to complete the first 3 missions of any campaign for the new units to show up? Also do I need to load this mod from the load mod option in the game?
Correct, you do the 3 first missions then you can get your units. And no, you don't need to get to the mod menu section to load the mod because the scripts are already being inserted into the original "Data" folder that you had to copy in order to make it work.