You can now allow people to login to you blog and leave comments with their Facebook account.
First step is to create an app on facebook.
Click on this link www.facebook.com/developers/createapp.php
Sign in to your Facebook account.
Fill in the name for the App. You can just put in the name of your blog if you want.
Hit agree then click on Create Application.
Next will be a security checkpoint.
Then on the left hand side click on Website.
Under Site URL put in the URL of your blog then hit Save Changes.
You will then get a screen that looks like this:
Make a note of the API Key and the Application Secret.
Go to your Blogs Dashboard.
On the left side scroll down to Settings>WP-FB AutoConn.
Scroll down to main options and put in the API key and Application Secret.
You have several options that you can click on for example you can choose to use facebook profile pics as avatars.
After choosing which options you want to add hit the Save button.
The go to Appearance>Widgets.
Under Available Widgets put your cursor on WP-FB AutoConnect.
Then drag it over to the Primary Widget Area and hit save.
This logo will appear in your side bar on your blog and will allow users to log in with their Facebook accounts and leave comments without having to register for your blog.
