To connect an Instagram account you must first connect the account to a Facebook page.
There are two methods of accomplishing this, and both are explained below.
Using Facebook's Page interface
1. On Facebook, navigate to the business' Facebook page.
2. Click Settings.
3. Click Instagram in the sidebar.
4. Click Log in.
5. Enter your Instagram credentials. Click Log In.
Using Facebook's Business Manager
1. On Facebook's Business Manager, click Business Settings.
2. Click Instagram in the sidebar.
3. Click Add.
4. Enter the business' Instagram credentials. Click Next.
Optional: Connect any relevant Ad accounts. If you do not wish to add one, click Skip.
5. Click Done.