I add mine at the time of writing. I first upload photos to an image-hosting website. I use photobucket, but there are others. You just sign up and follow the simple instructions. Then when i want to insert the photo into this message, click the icon above this text box that looks like two mountains and a sun. When you hover over it'll say "image instert:" then some computer text. When you click it another box comes up. On photbucket, once your photo is uploaded, click it and you'll get 4 options on how to insert it. I pick "direct link". Click it and it will say "copied". Then paste into the popped up box and then click "insert into message".
I use photobucket because there are other forum sites like this that I participate in were you also need an image-host so it's easy to use for all of them.