The first post in thread had a video of the steps, feel free to mute it. If you are using the pre-merged then it will not quite be accurate but you can start at about 1: 43 (YouTube Video). From 3:14 to 3:52 it will show how to move the "Put in Strive Game Files" folder and rename "backup" folder, SKIP this part if you have the pre-merged version.
Viewing post in Aric's Expansion Rebred
Chances are strong that you have the wrong folder path. But if you are unable to resolve it then I recommend joining the Strive Discord (https://itch.io/t/284398/discord), where we can walk you through the installation steps.