Follow steps below to add Four Square feature into your app:
Step 1 : Go to Appy Pie and click on Login
Step 2 : Enter your account details and login
Step 3 : If you have already created an app, go to Edit & Manage section of your selected app from My Apps and follow tutorial from Step 6, else click on Create New App
Step 4 : Enter Business Name and click on Next.
Step 5 : Enter Purpose of your app and click on Next.
Step 6 : Click on '+' and select view all to see all features
Step 7 : Enter Four Square feature name here
Step 8 : Click on the page to add it into your app