Additionally, once you connect your Pinterest and Facebook, every time you pin something on your pinboard, you are allowed to check a checkbox which automatically posts the Pins on to your Facebook timeline or page as well.
See: Logging Into Instagram With Facebook – 2019
How to Connect Pinterest with Facebook
Using any web browser sign in to your Pinterest account.
On the web page that comes up, click your user name or menu button (button with a pin symbol) at the top-right corner.
From the displayed list, click the Settings option.
On the next interface, click the Social Networks category from the left pane.
From the right pane, under the Social Networks section, click the Use your Facebook account to log in toggle button.
On the Facebook popup box, if prompted, provide your Facebook login credentials to sign-in.
On the Log in with Facebook page, click the Okay button at the bottom-right corner to connect to Facebook.
Back on the Pinterest settings page, finally click the Save Settings button from the bottom to apply the changes.
That is how to connect pinterest with Facebook account straight up!!!!