When I add a photo to an email, I am unable to write anything in the body of the email. What am I doing wrong?

The photo appears inline in the message body. To type above the photo, click just to the left of it to place the insertion point there, and press the Return key. This creates a blank line above the photo, where you can type. To type below the photo, click to the right of it and press Return.

You can also use the arrow keys to move the insertion point before the photo and then hit the return key.