You don't need to "activate the script", that was a legacy artifact of the RTW engine in EB1 which doesn't apply here.

There are two launcher icons, you should be using the Steam one (and delete the other one, since it's not applicable for your setup).

You need to download and apply Large Address Aware. It doesn't matter what the specs of your PC are, the game is limited to use only 2GB of RAM unless you adjust the executable with a compiler flag like LAA.