The instructions below are for users who have more data to copy into the Greyhole shares than their currently free space in the /var/hda/files/ folder.
Once One way to do that is to mount the shares that use the Greyhole storage pool, either on the HDA itself, or on a client computer on your local network, and copy your data from their existing location into the mounted shares.
This can be time consuming, but it is the safest way to use Greyhole.