Are you speaking about having the picture viewable in line with the rest of the post, such as the following?
If so, upload the picture to a photo host such as photobucket, flickr, webshots, etc.
Once it's uploaded you can post it inline by surrounding the link the the picture by IMG tags. In your post, the above picture would look similar to the following.
Code:
[ IMG]http://i5.photobucket.com/albums/y169/RhinoSS/mypicture.jpg[/IMG]