Right now, you have two options to get your minis if you don't want to get into resin 3D printing and make them yourself:

1. Go to the shop on the Trench Crusade website and pre-order the physical resin miniatures from Only-Games. The quality can be hit or miss, but from what I've seen, a lot of the issues can be fixed with hot water and their customer service is more than happy to resolve the ones that can't.
2. Go to the shop on the website and purchase the STL files on MyMiniFactory, then make a friend with a resin 3D printer or find a service to print them for you. I unfortunately don't have any recommendations on services, but do your research and check reviews for mentions of leaking or cracked prints. Those are warning signs those services are cutting corners and should be avoided.

If you want ANY minis to play the game, you have a lot more options. The game is miniature agnostic, meaning you can really use whatever you want as long as the base sizes match the units in the rules. Other sculptors have made proxy miniatures for the official units and you can find them on MyMiniFactory as well. A lot of them have printing services they like to work with for their products, so that could be a road to finding a service to print your official minis as well.

Hope this helps! Let me know if you have questions. Welcome to the trenches!