Docker storage setup

Brand new to docker just decided to switch from freenas because it was lacking support, have no clue what I am doing. currently have docker installed by following these instructions here and portainer from here however it appears that docker was installed to my primary hdd and not to the raid I have set up. Is there a way to configure docker to use a different storage system on install? Or am I just missing something basic in the settings, docker currently only using the 160 gb hhd it was installed on along with ubuntu server 16.04 instead of the 12 tb raid ie (/home/docker/containers_here and the raid which docker cant see /mnt/md0). Would appreciate any advice/help on the matter and apologize in advance for such a beginner question.