On my Nuc, I have two HDD's. The second is for storage and such. I want to use this hdd for my vbox .vdi. But when I go to search for it through vbox, my secondary hdd isn't listed. Is there a way I can add this?
In the details view for a VM, under storage, you can select a controller (usually SATA) and add a new storage attachment, in this case a hard disc (usually VDI). Clicking through the create dialog, you'll get to "File Location and Size". Clicking the icon to the right of the disc name, you'll get a standard file explorer window. So just navigate to your secondary HDD. To set the default, go to File/Preferences, and set "Default Machine Folder".