Use the edge of a plastic opening tool to peel the upper antenna off the headphone jack.

Use a pair of tweezers to remove the upper antenna from the iPhone.

Before reassembly, be sure to clean the metal-to-metal contact point on the upper antenna (not the mating halves of its connector) with a de-greaser such as windex or isopropyl alcohol. The oils on your fingers have the potential to cause wireless interference issues.