I will try to make it simple and easy to follow. No extra steps or configuration here, just the basic stuff which will get you going.

1- Go to developer page, and click on create app button, and follow the on screen instructions to create a new app.

2- Edit the page tab section with appropriate details. Also check out the App details section for privacy links and app icon if you wish to add one.

3- Enable sandbox mode for testing the app 1st.

4- Disable social discovery in Advanced section.

5- Add new testers and admins from Roles sections.

6- Now create a facebook page if don’t have yet OR use existing one to add the app to it.

7- Use the following URL to add the app:

https://www.facebook.com/dialog/pagetab?app_id=YOUR_APP_ID&next=YOUR_URL

Change YOUR_APP_ID and YOUR_URL, and hit enter. Select the page from the dropdown and click Add button. You are done, your newly created app will be on the page in tabs section.

YOUR_APP_ID = newly created app id, can be retrieved from the settings.

YOUR_URL = url to your app, hosted some where.

If everything is good and want to go live, just disable sandbox mode and enable social discovery and your app will be live for users.