The headphone jack cover screws in at the top of the case. This is really important as it keeps dust and water from getting inside. It needs to ALWAYS be screwed in when you are not using headphones.Unscrew it when you are ready to use your headphones. Be careful not to lose it. There is a Keeper that you can clip onto your headphone cable, so simply press it onto the headphone cable as soon as you unscrew it. Don't worry too much, however as there is a spare jack cover included and you can also buy more from www.lifeproof.com if it gets lost.You can plug in your Apple headphones directly into the headphone jack as most other headphone jacks are too fat to fit into the slim LifeProof case. We recommend always using either the General Use of the Swimming headphone adapters because they seal 100% of the water, dust, and other problems out of case.Just push the headphone adapter in until it stops, then screw it firmly closed. Now you can plug any headphone into the jack at the top of the adapter.To remove the headphone jack cover, simply unscrew it.Remember to take the headphone jack cover out of the Keeper and screw it back in.