To insert a photo in a message you need to have a hosting account so that you can put the address of the picture in the message. First you need to click on the "Insert Image" icon above. It is the third one from the left, in the second row above. It will insert a pair of brackets with the word "img" in between them. There are two sets and you will put your server address where the picture is located between the two.
You can also click on Additional Options below, and then "attach" a picture from your computer to the message. There is an attachment size maximum. See note after you click on the Additional Options below.
Hope this helps,
George