#1 Scale the image so it is not to large, i use: 900px X 650px.
#2 Upload your picture to a web server(somewhere else than Macrumors).
#3 Find the URL to view the image only(if its located in an other web page just right-click the image and select "view image" and copy URL from the address bar in the browser)
#4 Chose "reply" to the thread you want to wright in.
#5 Pressin the text editor.
#6 Past the URL where the image is located in the box that shows up.
#7 Post your reply.
Thanks for your help - that's great!