Select the drive you want to boot from and hit Enter.
IF IT WERE THAT EASY I WOULDN'T BE ASKING. HOW DO YOU SELECT WHICH ICON?
With the mouse.
WITH THE MOUSE OR WHAT? I ON A MAC TOP AND THE KEYBOARD CONNECTED TO IT DOESN'T WORK SO i GOT A USB ONE (VERSUS WIRELESS AS SOM EONE ELSE SUGGESTED) AND THE MOUSE IS WIRELESS AND ONLY SPPAERS A WATCH WITH NO POINTER. I'VE TRIED HOOVERING OVER ICON AND HAVE HIT ENTER AND NOTHING.
OK you never said that. I think you may need a wired mouse to make it work. Do you have one?
I DONT THINK SO A USB MOUSE?
ILL DO A QUICK CHECK AROUND BUT IT'S DOUBTFUL. anYTHING I SHOULD KNOW IN CASE I DON'T HAVE A WIRED MOUSE AS I WILL PROBABLY GO TO THE STORE LATER AND TRY THIS AGAIN AND DONN'T' EXPECT YOU TO WAIT?
Just bookmark this page or go to the link in the email you get.
If you can boot without the option key just go to System Preferences/Startup Disk and you can change it there.