Go here to create it: Create a facebook app
Good, your app is created. Now, make sure it knows where it's used: On the app's page, click "Edit Settings", then from the left navigation, click "Web Site". You should now see "Core Settings". Copy http://www.omyim24hr.com/ and paste it in the "Site URL" box. Now click "Save Changes". Done!
Get your app id and app secret from here: Facebook Application List
Select the application you created, then copy and paste the Application ID and Application Secret from there to the boxes below..