Thank you for your message and great to hear that you are using
https://www.map.army.
To change or update base maps in the WMTS or WMS format is only supported on individual deployed instances of map.army (pro) version. We do supply map.army to be deployed on closed networks. This is done on a project basis which includes all the required backend services.
Is the tutorial you are referring to the following:
https://www.youtube.com/watch?v=jV0iaUTjQlk?
If not, could you please send us the link to the tutorial.
Please do not hesitate to contact us, should the issue still occur on your side.
Kind regards
Martin from the map.army team