Well you need a "Package" installed to generate anything. There should have been some recommendations during the Stabilitymatrix installation.
You'll also need to have a Checkpoint, which contains all the data needed to generate images.
This must be in the directory: /stabilitymatrix/data/models/StableDiffusion
Here's an example with ReForge and Cyberrealistic XL 5.3 (on civitai.com)
If you have the package installed and a checkpoint in the Models directory, click left on the "Packages" and launch it.
This will take a while and open a window in your default web browser.
So if you can get an image with this, you can probably also follow other instructions to install any "LORA" or whatever is needed to generate images for this game.