Facebook is a very powerful social media. If you want to use facebook for your blog promotion then you have to follow the following steps:
First create your account at facebook.

Add friends by using friend finder feature.

Send updates of your website or blog to all your friends.

Try to establish personal relationship to all friends.

Join the relevent groups.

Post your blog or website link to the relevent groups.

If you follow these simple steps for blog promotion by using facebook then you would surely get good traffic from facebook.