gpt formatting and uefi booting

[Doll, Margaret Ann]

I have a Dell PowerEdge T120 with 12  4Tb disks.  I want to use the first
disk as the system disk and the remaining 11 as a raid 5.

I have the first disk set up as a raid 0.  I installed RedHat 6.4 server
software on the first disk.  I set up the Dell to use a uefi boot instead
of bios.  However, I cannot boot up the new system as the bios does not
support the size of the system disk.

I gather I should set up  gpt partitioning instead of the default mbr on
the first disk.

How do I do this?