docs: installation how-to

Signed-off-by: Jan Larwig <jan.larwig@digits.schwarz>

Author: tuunit

README.md

@@ -34,6 +34,24 @@ Please see our [book](https://stackitcloud.github.io/cluster-api-provider-stacki
 
 Use `make serve-book` to serve the book locally from this repository.
 
+## Install with clusterctl
+
+Create `clusterctl.yaml` with the published release URL. Replace `<version>`
+with the release tag you want to install.
+
+```yaml
+providers:
+  - name: stackit
+    url: https://github.com/stackitcloud/cluster-api-provider-stackit/releases/download/v<version>/infrastructure-components.yaml
+    type: InfrastructureProvider
+```
+
+Install the provider:
+
+```sh
+clusterctl init --config clusterctl.yaml --infrastructure stackit
+```
+
 ## Launching a Kubernetes cluster on STACKIT
 
 Check out the [Quick Start](./quick-start.md) for launching a cluster on STACKIT.

docs/src/SUMMARY.md

@@ -7,11 +7,11 @@
   - [Classic Cluster Template](usage/cluster-template.md)
   - [ClusterClass](usage/clusterclass.md)
   - [Workload Addons](usage/addons.md)
-  - [clusterctl](usage/clusterctl.md)
   - [Workload CNI](usage/cni.md)
   - [Upgrade](usage/upgrade.md)
   - [Cleanup](usage/cleanup.md)
 -->
+- [clusterctl](usage/clusterctl.md)
 - [Topics](./topics/index.md)
   - [OS Images](./topics/images.md)
   - [Accessing VM instances](./topics/accessing-vm-instances.md)

docs/src/usage/clusterctl.md

@@ -1,22 +1,28 @@
 # clusterctl
 
 Each release publishes `infrastructure-components.yaml`, `metadata.yaml`, and
-cluster templates as GitHub Release assets. Install a published version with:
+cluster templates as GitHub Release assets.
 
-```sh
-clusterctl init \
-  --infrastructure \
-  https://github.com/stackitcloud/cluster-api-provider-stackit/releases/download/v<version>/infrastructure-components.yaml
+## Install a published release
+
+Create `clusterctl.yaml` with the published release URL. Replace `<version>`
+with the release tag you want to install.
+
+```yaml
+providers:
+  - name: stackit
+    url: https://github.com/stackitcloud/cluster-api-provider-stackit/releases/download/v<version>/infrastructure-components.yaml
+    type: InfrastructureProvider
 ```
 
-Or latest:
+Install the provider:
 
 ```sh
-clusterctl init \
-  --infrastructure \
-  https://github.com/stackitcloud/cluster-api-provider-stackit/releases/download/latest/infrastructure-components.yaml
+clusterctl init --config clusterctl.yaml --infrastructure stackit
 ```
 
+## Use a local provider repository
+
 For local development, package the provider as a local clusterctl repository:
 
 ```sh