Here's how I do it, but not sure if it's the best or easiest..... I take the pic with my phone. I then e mail the pic back to me. I save the e mailed pic. When it asks what size, I use medium. I then go to the post, click on add attachment, it asks from where, I choose my photo library, I choose the pic I just e mailed to myself. Choose the medium size. The pic will show up below in a tiny square where you added it as an attachment, not in the actual area you type. When you "post" it will then show up. Go back in and read the post you just made and it should be there.
If you just pick a photo from your phone it will be to big of a file. You have to reduce it. That's why I e mail the pic back to myself and save it. Then it gives me a size option when I attach it on the boards. Now I'm sure you are totally confused!!!