You need to boot into recovery before erasing the thing (your hard drive I assume) as explained here (you need to be booted from something other than your hard drive because you can't erase your startup disk while booted from it):
OS X Yosemite: Erase and reinstall OS X
Those instructions are for Macs with originally came with Lion or later. If yours originally came with Snow Leopard or earlier, you'll need your install disk.
Also, depending on the age of your Mac, you may need to use internet recovery (which means you will be connecting to Apple's servers), and that would be activated by using Command + Options + R.
FWIW, your link only leads to a sign in page for Google drive.