For instructions, see Using UEFI and the BIOS Setup Utility.
The Boot Option Priority list shows the current boot order from top to bottom. For example, the first device in the list indicates the first boot option.
For example, if you want to move a device to the second slot, select the second item in the list.
The device you selected is moved into the indicated slot, and BIOS reorders the remaining devices to accommodate the change.