How to Follow Your Facebook Friends on Instagramby Micah McDunnigan
Like any social network, Instagram isn't much fun to use if you aren't connected to other users on the site. If you already have a Facebook account with a substantial Friends list, then you can probably find enough Instagram users to get your photo sharing social network started. When you connect your Instagram account to your Facebook profile, Instagram will provide you with the option to follow all your Facebook friends that use Instagram.
Open the Instagram app on your smartphone. Tap the farthest right button along the bottom of the screen to go to your profile and then tap the Settings icon at the top right. This icon will look like a gear on iPhones, and a line of three dots on Androids.
Tap on "Find & Invite Friends" from the list of options and then tap "Facebook Friends."
Follow the instructions in the pop-up to authorize Instagram on your Facebook account, if prompted. When done, your device will return you to the Instagram app where a list of your friends who use Instagram will be displayed.
Tap the "Follow" button next to each user you want to follow.