- Close down Asset Forge before you do this.
- Download the OBJ version of the pack you want. e.g. this Ultimate Modular Sci-Fi pack
- Unzip the folder and name it something meaningful, I use a letter to remember where I got the asset from (pictured).
- Open the folder you installed Asset Forge into, and there should be a folder called "Collections".
- Move the pack to that folder.
- Relaunch Asset Forge.
- Voila!