Is it possible to have an option in the grub boot menu so that I can boot from a usb.
If it is, could I have some guidence on how to go about it.
Thank you
If this is an older computer with legacy BIOS booting, you might be able to chainload. If this is a newer computer with UEFI booting, then it is better to use the UEFI firmware (or BIOS) facilities to boot the USB drive.
You could try plugging in the USB drive, and then running (as root)
grub2-mkconfig -o /boot/grub2/grub.cfg
and see whether this automatically adds a boot menu entry.
I remember trying something like that a few years ago. And it did not work. I had to hit F12 during boot to get the BIOS boot menu, and then I could boot the USB. But if I did it from grub, it failed. In some of the newer computers, the BIOS does not initialize most USB devices, in order to give a faster boot time.