download and install the GIS software:
https://www.qgis.org/en/site/forusers/download.html
I'm not on the most latest version so hope this is ok for you to follow.
once you get it running and open it, you start with a blank project.
There should be a browser section where you manage data sources. Find XYZ Tiles, right-click and new connection.
This example just adds a simple google earth imagery tiles into your project. But you can get as complicated as you want.
for example, I bring in a transparent shaded relief from other sources and stuff like 12 mile territorial and EEZ boundary lines.
in the XYZ Connection dialog box name it Google Earth. then enter the URL as
https://www.google.cn/maps/vt?lyrs=s@18 ... y={y}&z={z}
Min Zoom level 0, max zoom level 18
Add layer to project and confirm you're seeing the tiles rendered in the map display and that you can zoom in with increasing detail.
QGIS should have a Processing Tool Box that can be turned on under the Processing drop down. In the Processing Toolbox, there's 'Raster tools'.
Expand it and launch Generate 'XYZ tiles (Directory)'
this will generate the png tiles that you'll place in your Stamen Terrain cache.
the extend can be based on the current extent of you map view, or use my coordinates here.
2812651.7191,4596260.8876,5368707.9957,6546050.9136 [EPSG:3857]
or test with a smaller area...
Do tiles of PNG at 256x256 like I'm showing in the attachment. I'll also enter a background color (#d7d8c7).
pick a local drive location to stage the output. I think it took my system like 20-30 minutes processing time.
When its done you should have the file structure and image tiles where you saved it. then copy it into:
\Command Modern Operations\WW\Cache\Stamen Terrain\
because they're limited to 256x256 they're not the sharpest images once in game, but good enough.
looking forward to trying the scenario.