I just used the following video , which includes a download. The video instructed me to type these codes in terminal, which I did.

cd Downloads/
chmod 755 *
./fastboot-mac oem unlock.

Then I unlocked it on my Nexus 10, so I think that worked. But i selected start on the device and it got stuck in booting. After restarting a lot, it always does the same thing. Help please?