MAINT: document how to build the image

README_SETUP.md

@@ -6,6 +6,15 @@ See [docs](docs.indiscale.com) or `INSTALL-GIT.md` for information on how to ins
 
 Want to try it out?  Try these steps:
 
+## Building the image
+You can build the docker image using the `docker` command in the `docker` folder:
+```sh
+cd docker
+DOCKER_BUILDKIT=1 docker build -t caosdb .
+```
+The buildkit setting allows the usage of some special features in the `Dockerfile`.
+
+The image will be named `caosdb`.
 
 ## Certificates