the following ways:
- At the top, just click on it 'Login with Facebook'
- Then, for the first time. going towards the confirmation page of Fb. select the 'Okay'
- After that no adjustment of data
   username (in this section once you register with your facebook account).
   "Username can be replaced or the same as the name on facebook, it's up to you"
   continue to adjust what you want. whether the data used in the facebook / import in forum
then click the 'Save / Register'

- After that, ... (you've successfully logged in and registered), including your profile picture avatar in the forum
*note: the term 'profile picture' on facebook, if at the forum called 'avatar'

and then
- You get the message / inbox, providing a forum account password.
besides can directly login with facebook, your username and password can be login usual (without via Facebook)
- If necessary, you can change the password, avatar, etc.