How to Install an iFrame Application on Your Business Facebook Page
If you have created an iFrame app for use in your marketing campaign, you will need to install it on your Facebook Page. You can go to the Developer page, select your app in the Recently Viewed section of the left sidebar, and then click the Edit App button in the top-right corner.
To add the application to your Facebook Page, find your 15-digit app ID/API key at the top of the App page and then follow these steps:
Type the following URL in your browser window, using your app ID and replacing YOUR_APP_ID with the 15-digit app ID/API key:
You’re taken to the site where you add your app to your Page.
From the Add This Application To drop-down menu, choose the Page where you want to add your app.
Click the Add App Name button.
Now your iFrame app is added as a custom tab to your Page. You can navigate to your page and change the position of your tab just as you would any tab.