how do i set my phone to auto rotate my photos when i turn my phone around?

Try unlocking the auto-rotation. Go to your multitasking bar (double tap Home button), then swipe from left to right. There should be a symbol there that looks like a circular arrow with a lock in there. See if it's 'locked'.

It does so automatically without any setting for it - unless you have portrait mode locked on your iPhone.

It should do it automatically. Assuming you mean the photos in your camera roll.