FYI, I can't figure out how to post from my phone either. I take phone with phone email to myself. save and reduce size and save a final copy to my Photos File by year. Then when I want too post I retrieve it from my laptop and attach to my message.
I have to say it took a while for me to figure out how to post from my laptop, but now it is second nature. I do have written directions if any one wants them.