You might have to update your Facebook on your phone. Or you just go onto make status and there should be a little camera that says Picture. You hit that and then you hit choose photo. And then you just pick which photo you want and post done then post.
If you have the Facebook app in your phone, then open the app and tap the Photos icon at the bottom of your screen. You can then add a photo to Facebook by choosing a photo from the camera roll or by taking a photo.