Enter an Application Name, and make sure you agree to the Facebook terms.
You will be taken to the page that controls your application's settings.
Under the Website tab, note the Application ID and Secret.
Plug these values into the top of facebook.config.php for the FACEBOOK_APP_ID and FACEBOOK_SECRET constants.
Also inside facebook.config.php set BASE_URL constant.
Under the Website tab, set the Site URL to your web page's base URL. Example: http://www.preview.noahthemes.com/Facebook/ The trailing slash is required.
Under the Facebook Integration tab, set the Canvas URL to your web page's base URL. Example: http://www.preview.noahthemes.com/Facebook/ The trailing slash is required.
Click Save Changes.
Upload facebook folder to your root folder where index.php file is.
Go to your_site_name/facebook/install.php
Using the plugin
Edit layout.tpl.php of your current theme and place link where you think is best for you. Or you can add link using additional contents (Control panel » Contents).
Or may be a custom fields will be better ?!? You decide !
Example: <a href='facebook/' title='login with facebook'>Login with facebook</a>
Example: <a href='facebook/' title='login with facebook'><img src='link to facebook image' alt='login with facebook' /></a>
