If you've linked your Instagram account to your Facebook account or registered on Instagram using your Facebook account, you have the option of sharing your photos and videos with your family and friends on Facebook. When you post something from Instagram on Facebook, your Facebook friends will immediately know that you are on Instagram because Instagram posts are visible by default. You can't change the privacy settings from Instagram, but you can configure Facebook to make your Instagram posts private.
Log in to your Facebook account, click the gear icon and choose "Account Settings" from the menu to access the General Account Settings page.
Click "Apps" in the navigation pane to view all apps installed on your Facebook account. Instagram posts your updates to Facebook through the Instagram app.
Click the "Edit" link next to the Instagram app to change its settings.
Choose "Only Me" from the "Visibility of app" drop-down box to make all Instagram posts private. Only you can see your private Facebook posts.
Click the "Close" link and then return to your Facebook profile by clicking the Facebook icon.