Note that personal Instagram pages linked in this way become Business Instagram pages.
How to connect an Instagram account to your Facebook Business Page.
Log in to Facebook, then switch into the Page that you want to connect to your Instagram account.
From your Page, click Manage.
From the left menu under Professional dashboard, click Linked accounts.
To connect an account, click Connect account. Enter your Instagram account's username and password, and select Log in.
We also have a video tutorial that demonstrates this process, which you can view below.
For more information on this, visit: https://www.facebook.com/business/help/898752960195806