Guide

1. Make sure you have Forge 1.12.2 version 2859 installed. If you do not, you can install it here (install client side only, if it does not open you need to download java). 

2. Install modpack if you have not done so already. This can be done here

3. Open Minecraft Launcher, and create a new instance of 1.12.2 Forge 2859. Allocate at least 12gb of ram for stability (click more, go to arguments and change the 2 in "-xmx2g" to 12.) 

Optional: Create instance in a new location for a clean install

4. Go to the install location and drag over the "resourcepacks" and "mods" folders.

Optional (but recommended): move the IR packs from "resourcepacks" to "config\immersiverailroading" (you will need to create these folders if you have not run the game before)

5. Start the game, the game may not respond for a long amount of time on the first ever start as it builds the cache, that is normal.

6. Load the resource packs if you did not move them to "config\immersiverailroading\"