update README to describe how to use custom config

Author: deitch

README.md

@@ -44,13 +44,20 @@ To deploy a cluster via the cluster-api:
 
 #### Initialize the Cluster
 
-To initialize the cluster:
+To initialize the cluster, you need to provider it with the path to the config file.
+
+1. Download the clusterctl config file for your release.
+1. Use the config file.
 
 ```
-clusterctl --config=https://github.com/packethost/cluster-api-provider-packet/releases/latest/clusterctl.yaml init --infrastructure=packet
+VERSION=v0.3.0
+curl -L -o clusterctl.yaml https://github.com/packethost/cluster-api-provider-packet/releases/download/${VERSION}/clusterctl.yaml
+clusterctl --config=./clusterctl.yaml init --infrastructure=packet
 ```
 
-We are in the process of working with the core cluster-api team, so that you will not need the
+Unfortunately, clusterctl itself does not support passing a URL to `--config`, see [this issue](https://github.com/kubernetes-sigs/cluster-api/issues/3099).
+
+Additionally, we are in the process of working with the core cluster-api team, so that you will not need the
 `--config=` option, hopefully soon.
 
 #### Generate Cluster yaml
@@ -71,7 +78,7 @@ To generate your cluster yaml:
 1. Run the cluster generation command:
 
 ```
-clusterctl --config=https://github.com/packethost/cluster-api-provider-packet/releases/latest/clusterctl.yaml config cluster <cluster-name> > out/cluster.yaml
+clusterctl --config=./clusterctl.yaml config cluster <cluster-name> > out/cluster.yaml
 ```
 
 Note that the above command will make _all_ of the environment variables required. This is a limitation of