where do I specify the canvas page/name? (not the canvas URL)

I am new to face开发者_StackOverflowbook apps, developing a simple Javascript app. I know I must be missing something big, but I can't see anywhere on the app settings where do specify the canvas page. all the screenshots I see online include it but not mine, I attached it here:

Edit: For the Page Tab section to appear, click the white box that is under the Mobile and Devices section that says "I want to build a custom tab for Facebook pages".

The following has worked for me in the past:

Website: put the full URI without the filename and the domain in the site domain textbox:

Site URL: http://www.yoursite.com/subdomain/
Domain: yoursite.com

App on Facebook: put the same path as in the previous

Canvas URL: http://www.yoursite.com/subdomain/

(You will also need to add a https://... url by September I believe)

Page Tab: finally include the full URI with the file name

Page Tab Name: Your tab name
Page Tab URL: http://www.yoursite.com/subdomain/apage.html

This is specified on Getting Started › Apps on Facebook › Canvas Tutorial

To set up your Canvas Page and Canvas URL you must first register your Facebook app and enter in your basic app information. Add an App Namespace to create a Canvas Page URL.

Also when you click on the [?] next to App Namespace when editing your application it also says

Namespace for your app used for Open Graph and Canvas Page (if applicable)