how can i enable my dell e 6540 to bbot from my 2nd SSD (placed in a caddy - replaced my dvdrom)

i replaced my dvd-rom with an caddy to add another ssd to the system.

i moved my sdd (win2012) to the caddy and put my new ssd (win2016) as internal.

i can easily boot from internal disk, then i also can Access my 2nd disk in the caddy.

i would like to be able to chose at start from which ssd i boot - is there anyway?