1. Add from the Instagram App
Open the Instagram app → Select 'Edit Profile' → Under Public Business Information, Select Page → Choose a Page from your Pages that you'd like to connect to or select 'Create a New Facebook Page' → Done.
2. Add from the Facebook site or App:
On the sidebar, under Explore, click Pages > Click the name of the Facebook Page you want to work with > Settings > Instagram > Log in to your Instagram account > Enter your user name and password and click Log In.
3. Exit the app from the background mode and reopen it again. Open left menu → Click Profile to make sure that your Instagram account has been added.