Following are the setups to get Facebook app id.
Search Meta for Developers on google.
Click on Login in option from the meta for developers page, where you need to login with your Facebook account.
After you login, click on “My Apps” and you will come to your apps created.
Here, in your app created, there is “App Id”, just copy that and login to app.whatso.net
On whatso dashboard, click on “API Setup” on left hand side nav-bar, and there paste your “App id” in “Facebook App Id” textbox and click on “Submit”.