Well if they are just plain headphones then you just need to plug them into the right one. If they are, however, headphones with a microphone attached, then you have an issue.
There would be two fixes... well three...
1. Get a headset/mic combo that has two plugs.
2. Get an adapter that can split you singular one up to use both jacks.
3. Get an adapter that will take it from a 3.5mm jack to a USB one.
Personally I like option 3 as it tends to get better results.