Don't ask me how, but when I take pics with my I phone or I pad & they post sideways, here's what I do. Use the edit button. Go to the icon that spins the pic around & resizes (it's the second from the top on the left on my I pad). Spin the pic all the way around. If the "done" icon is not lit, just resize a tiny bit & it'll appear. Click "done" & try posting the pic. Mine will be rightside up after those shenanigans are done! Like the pics below. Those are some kumihimo & knitted jewelry strands I made the past week :)
