add usage instructions to README.md

Author: Markus Schwer

README.md

@@ -1 +1,28 @@
-# DevPod Provider STACKIT
+# DevPod Provider STACKIT
+
+<!-- markdownlint-disable-next-line MD013 MD034 -->
+[![Go Report Card](https://goreportcard.com/badge/github.com/stackitcloud/devpod-provider-stackit)](https://goreportcard.com/report/github.com/stackitcloud/devpod-provider-stackit)
+
+Run [DevPod](https://devpod.sh/) on [STACKIT](https://www.stackit.de).
+
+## Usage
+
+To use this provider in your DevPod setup, you will need to do the following steps:
+
+1. See the [DevPod documentation](https://devpod.sh/docs/managing-providers/add-provider)
+   for how to add a provider
+2. Use the reference `stackitcloud/devpod-provider-stackit` to download the latest
+   release from GitHub
+3. Configure the provider by specifying a few options:
+- Region
+- Project ID
+- Availability zone
+- Disk size
+- Private key path
+- Service Account key path
+
+### STACKIT Service Account
+
+To authenticate with STACKIT you need to create a Service Account, generate a keypair locally and upload the public key
+and download the Service Account Key JSON.
+See the docs to see how: https://docs.stackit.cloud/stackit/en/create-a-service-account-key-175112456.html