4. Press the "Share" button, share the long URL to Google URL Shortener and generate a shortened URL.
When you read the tag with your phone, you will a share dialog for your website. However, the dialog is the desktop version, instead of the mobile version of Facebook. It might not look well but when people press the "Share" button there, your website will be posted to their timeline.
I used the desktop version, by including the "m2w" element in the URL, as the mobile version of Facebook doesn't support sharing with this kind of URL. In case Facebook support it later, we will just need to add "facebook.com/sharer/sharer.php?u=" in step 3.