Here's how to connect your Instagram account to a Facebook account:

Step 1: Navigate to your Instagram profile, and select the three bars in the upper right hand corner:

Step 2: Select the "Settings" tab in the list of options. 

Step 3: Select the “Account” button.

Step 4: Select the “Linked Accounts” option. Make sure you are logged on to the Facebook you wish to link your Instagram account to.

Step 5: Select “Facebook” when given what pages you want to connect to your Instagram page. Make sure that the Facebook account that you want to connect is displayed.

Step 6: Select “Continue as…” and you will be taken back to the main settings with your Facebook connected.

Your Instagram is now connected to a Facebook account! 🎉 You can unlink the accounts at any time by removing them from the "Linked Accounts" tab in your settings.

For more information, check out this link or to troubleshoot your Instagram and Facebook connection.