change --hostname to --create-hostname in docs

docs/installation_instructions.md

@@ -138,7 +138,7 @@ There are two options to create a cluster:
 
 2. By creating a new VPS through the API, using the `--create-droplet`
    argument
-   - Make sure to also provide the `--hostname` and `--ssh-key-id` arguments.
+   - Make sure to also provide the `--create-hostname` and `--ssh-key-id` arguments.
 
      You can find your SSH key ID by going to VPS Cloud -> SSH keys and
      checking the link under "Show key". The numerical part is your SSH key
@@ -160,7 +160,7 @@ There are two options to create a cluster:
 - Here is an example of a complete creation command:
 
   ```
-  $ python -m openappstack my-cluster create --create-droplet --hostname oas.example.org --ssh-key-id 112 --create-domain-records --subdomain oas example.org
+  $ python -m openappstack my-cluster create --create-droplet --create-hostname oas.example.org --ssh-key-id 112 --create-domain-records --subdomain oas example.org
   ```
 
   > **NOTE:** You can use the `--acme-staging` argument for testing purposes