Improve readme

README.md

@@ -11,9 +11,35 @@ Builder for [OSTree](https://ostreedev.github.io/ostree/)-based operating system
 
 See [this blog post series for background information on the PoC and its motivation](https://blogs.sap.com/2023/07/10/making-an-immutable-image-based-operating-system-out-of-garden-linux/).
 
+Refer to [the Garden Linux README for setup instructions for the Builder](https://github.com/gardenlinux/gardenlinux#build).
+
 This repo contains two os builder definitions.
 
 The `debian` directory contains a build for a debian trixie image.
+It takes packages from the Debian apt repositories.
+
+To build it yourself, run inside the `debian` directory:
+
+```bash
+# Optional: To build the OSTree Repo
+$ ./build ostreeRepo
+# To build the bootable image
+$ ./build ostreeImage
+```
+
+> [!NOTE]
+> The `ostreeImage` will download a copy of the OSTree repository from the Garden Linux artifact storage.
+You don't need to run `ostreeRepo` locally.
 
 The `gardenlinux` directory contains a build for a gardenlinux today image.
+It takes packages from the Garden Linux apt repositories.
 This directory contains a lot of code taken from the [gardenlinux/gardenlinux](https://github.com/gardenlinux/gardenlinux) repo.
+
+To build it yourself, run inside the `gardenlinux` directory:
+
+```bash
+# Optional: To build the OSTree Repo
+$ ./build kvm_dev_curl-ostreeRepo
+# To build the bootable image
+$ ./build ostreeImage
+```