A minishift openshift cluster can be created with cluster metrics installed. Although I couldn't find a way to add metrics to an already created minishift VM instance, the steps below helped to get a new instance up and running easily.
Step 1 - Initialise minishift with metrics.
Create a fresh minishift VM with an openshift cluster using the below command. The --metrics parameter is the only additional thing I had to provide for minishift to start installing cluster metrics and Hawkular.
$minishift start —metrics