Click or use the Peek and Pop? [on hold]

As we know that Peek and Pop have been one of the 3D touch highlights in the Apple's lineup of iPhone 6S/7/8/X.

How can one add discoverability on the UI element in an app for the user to know that Peek and Pop is possible over that element?

P.S: At times Peek and Pop isn't available for the element when the user expects to have it on.