How do I set user restrictions on Freenas?

I'm using freenas for my storage server but I'm having trouble trying to use the user and groups option. I want to give myself full access to 3 HDD in the server and give everyone else access to only 2 of the HDD. How do I go about this?

Forgive me for having to pull this out of long-term memory, but the last time I ran into FreeNAS was back in February when we were doing an eval at the office. IIRC there's no easy way of doing ACLs or the like. Access control for data is/was a two-step process:

1) Enter the groups & users via the GUI
2) Drop down to shell and use chown and chmod to control the access to the filesystem

In short, it winds up being essentially the same as on any unix box out there, save the monowall-looking GUI stepping in during some jobs. What you're trying to accomplish isn't that hard, though I wouldn't try restricting access to drives/devices. It would be a better idea to think through how you want users to view/access the data the NAS box will provide and setup the filesystem accordingly. For giggles I just checked the roadmap - GUI config of user access is set for 0.7, so it's not there yet.

I've never used Unix, I'll have a look into those commands and settings. I did find something in a guide about that but the guide wasn't very clear.

If you're unfamiliar with UNIX concepts and the shell, the best place you can start is to sit down with the FreeBSD Handbook. FreeNAS, for the most part, is based off FreeBSD 6.2, so the documentation is still good. The 3rd section on UNIX basics will get you headed in the right direction. When you're more comfortable with the filesystem concepts and the shell you can start looking into specific commands. The high level overview is that chown is CHange OWNer and does just that for files and directories. chmod is CHange file MODe, and controls access to particular files and directories. Section 3.3 is your friend, here. Don't be afraid, it may seem arcane but it's actually easier to use than Windows permissions.