Then this part is easy ...
When you type your reply to this message, look at all the buttons above the text box. One line has formatting information - Bold, Italics, Underline etc - the next line is for adding photos and links to websites and the like. The second button from the left is a square which is suppose to be an image of a photo, meaning that is the button to push if you want to add a photo to your post.
Take a look and see if you can see what I'm talking about ...