one way is to leave I want to preview my post and/or attach a file
checked then it will have a place to choose file to attach file must be resized small enough to be allowed.

Other is to go to Photobucket.com join upload your photo there click the photo and there will be a links box to the right click the IMG line (second from bottom) the come hear and paste in your post Ctrl V or use paste in browser and line shows up and will show as a picture after you post