Go to your photos and in the top right hand corner press 'edit'. You can then tap on which photos you want - you will see a green 'tick' on the photo. You then tap on 'share' on the left hand corner of the screen. It will come up with email, twitter, Facebook etc., so you tap on Facebook and you can then post your pics.
Another way of doing it is to tap on the individual photo you want to send, then in the top right you will see an arrow - tap on that and the Facebook icon will come up and you can post it like that.