What do i do if i didn't download a battlenet authenticator and i have to put in an authentication code?
This depends whether someone with a WoW account that does have
an authenticator attached has logged into your game. If so, simply
log in normally but leave the authenticator field empty. It will
then log in normally.
If not, or the above does not help, contact Blizzard customer
support. There is a chance someone got hold of your account
details, added the game to their account and/or attached an
authenticator. When this happens, you can no longer log in to the
game or your account.