If you have account on Parse than follow step6 or start from beginning. Step1: SignUp in to Parse.com, here is a link for signup into parse https://www.parse.com/#signup.
Step2: Enter Your App Name and click on “Create App”
Step3: After creating app you will get you Application Key.
If you can not find your application and client key than go to “Dashboard” and click on “Select an App”
Step4: Now click on “Setting” and than “Key” here you can get every key that is related to your app
Step5: Here you can get your Application Key and Client Key.
Register Facebook Key Into Parse
Step6:click on “Authentication” and check “Allow Facebook authentication” , make it “YES”.
Enter your facebook App id and secret key.