GPL AMI CentoOS Virtualmin - disk space issue for /sda1 vs /sdb


I am new to virtualmin on ec2. I would like to use the full amount of HD space available to a small instance and by default / is mounted /sda1 with 10GB only whereas /sdb has the full 140GB available. I may be missing something very simple as far as how ec2 works but any tips for expanding the root or available space to my created virtual servers over the 10GB that exists?

I could do a new mount from /sdb and move everything over, any help would be appreciated