http://www.facebook.com/developers/

Add the Developer app like you would any other application. When you get inside, you’ll see a button that looks like this:

After you’ve clicked the button, you’ll come to a Page where you’ll need to input your application’s name and agree to the FB Platform TOS to continue. It will look like this:

Give your application a name, click “Agree”, and then “Save Changes”. Next you’ll see the Edit screen, on the Basic section. It currently looks like this:

This page contains some very important information, such as the API and Secret Keys and your application ID, so take note of their location under the ‘Basic‘ tab. You can also put something in the ‘Description’ field if you have something in mind, or fill this field in later. After you’ve looked things over click on the Canvas tab to configure the remaining fields that are essential to get your application running. The Canvas section looks like this:

You will need to look at four key settings here. First, is the Canvas Page URL field. In this field you will have to create a unique Canvas Page URL. Find out what your Canvas Page URL will be before moving on. Next, look at the Canvas Callback URL. This is the location where the application will be hosted on your server. For example, http://www.yourserver.com/yourapplication, where the application files would reside in the ‘yourapplication‘ folder on the domain ‘yourserver.com‘. The next two fields to look at are the Bookmark URL and Post-Authorize Redirect URL fields.  Here you can input your full Canvas Page Url. An example of this would be http://apps.facebook.com/yourappname/ in the situation where you chose ‘yourappname‘ in the Canvas Page URL field above. You can also input the URL of your application’s invite page URL in either of these fields if you’d like user’s to be directed there each time they use the application.

When you’re done configuring these settings, click ‘Save Changes’ to continue. Now you’ll need to make a few quick changes to your application’s files and upload them to your server. After that your app will be up and running!