Completed install docker section.

README.org

@@ -89,8 +89,18 @@ gcloud compute instances create $gcp_machine_name --zone australia-southeast1-a
 
 * Step 3 - Install docker on virtual machine
 
-Coming soon...
+Next up we need to install [[https://docker.com][Docker]] on the newly created virtual machine so that we can then deploy Gitlab as a container.
 
+By default the virtual machine operating system for the vm we created on GCP is [[https://debian.org][Debian]]. There are instructions for installing Docker on a debian machine [[https://docs.docker.com/engine/install/debian/#install-using-the-repository][here]].
+
+#+begin_src bash :shebang #!/bin/bash :tangle 4-install-docker.sh
+    # Retrieve the vm name
+    export gcp_machine_name=$(gcloud compute instances list --limit=1 --format='value(name.basename())')
+
+  # Connect to the machine using ssh
+  gcloud compute ssh $gcp_machine_name --ssh-key-file ~/.ssh/$USER -- "curl -fsSL https://get.docker.com -o get-docker.sh && sudo sh get-docker.sh"
+
+#+end_src
 
 * Step 4 - Install gitlab via docker