It is more likely in the Hard Drive BBS Priorities. If it is there than you have to make that one first. Then go to the boot option and do the same thing in there too. Plus one other thing is you have to have the USB devise plug in too for it to see it. You might not have that option till it is plug it.
BIOS Features
Boot Option Priorities
Specifies the overall boot order from the available devices. For example, you can set hard drive as the
first priority (Boot Option #1) and DVD ROM drive as the second priority (Boot Option #2). The list only
displays the device with the highest priority for a specific type. For example, only hard drive defined as the
first priority on the Hard Drive BBS Priorities submenu will be presented here.
Removable storage devices that support GPT format will be prefixed with "UEFI:" string on the boot device
list. To boot from an operating system that supports GPT partitioning, select the device prefixed with "UEFI:"
string.
Or if you want to install an operating system that supports GPT partitioning such as Windows 7 64-bit, select
the optical drive that contains the Windows 7 64-bit installation disk and is prefixed with "UEFI:" string.
Hard Drive/CD/DVD ROM Drive/Floppy Drive/Network Device BBS Priorities
Specifies the boot order for a specific device type, such as hard drives, optical drives, floppy disk drives,
and devices that support Boot from LAN function, etc. Press <Enter> on this item to enter the submenu that
presents the devices of the same type that are connected. This item is present only if at least one device
for this type is installed.