Your Instapage page can be published to your Facebook page as a tab, allowing you to grow your mailing list right within Facebook.
Note: This only works on Facebook Pages, not profiles, as Facebook only allows custom tab applications on Pages.
Only the mobile version of your landing page will be published to Facebook.
After you have finished editing and saving your Instapage page, click Publish.
Finally, select the Facebook option.
Make sure you disable any ad/pop-up blocker you might have installed on your browser.