Need help with Geomerging in W3 Model Editor

[azurespecter]

I'm doing a personal project and I'd like to combine some existing models (user created models)

So I downloaded the War3 Model Editor, and looked at every tutorial/guide I could find... however they are all outdated. I can find the .mdx files and import one model, but can't seem to find a way to import a second model so I can merge the two. I also can't find out how to export. To make matters worse, the readme is an outdated web page, so I can't really figure this out on my own.

So if anyone can point me in the right direction, I'd appreciate it! Thanks