Open “Facebook for Developers” on your internet browser. Type developers.facebook.com in your browser’s address bar and hit ↵ Enter on your keyboard.
If you aren’t automatically signed into Facebook on your browser, click the Log In button in the upper-right corner of your browser window and log in with your Facebook account.
Click the My Apps button. It’s located next to your profile picture in the upper-right corner of your browser window. It will open a new page with a list of all your apps.
Scroll down and find your app or website. If you’ve already integrated Facebook into your app or website through the Facebook for Developers page, you will see it here. Scroll down to browse the list or use the Search field at the top to quickly find an app.
Note down the App ID. You will see the 15-digit App ID right below the app’s name. This number is unique to your app. You will need your unique App ID when you’re using analytics, or creating ads in the Audience Network.
Click + Add New App. This is the green button in the upper-right corner of the My Apps list. If you have an app or website that you want to integrate Facebook into, click this button to get started. It will open a pop-up dialogue box.
Enter a Display Name. This is the app title that you will see on your My Apps list when you log into the Facebook for Developers webpage.
Enter a contact email. Facebook will use this email address to contact you about your app.
Click Create App ID. This is the blue button in the lower-right corner of the pop-up dialogue box.
Complete the captcha. You will need to complete a quick captcha task to prove you’re not a computer bot.
Note down your new App ID. You will see your unique, 15-digit App ID associated with this Display Name in the upper-left corner of your window.