you first upload the pic to NS or another image hosting site, then you right click your uploaded image and chose copy image location. then in the reply box (assuming you have fancy editor off) you copy past the image address in between the image tags so it looks like this
there ya go! but there is a multi page thread about this in site discussion so you should of searched first
What I do so that I don't have to bother with links is to upload my pics to ns in my private gallery. From there you can just copy and paste each one into the thread body. No link messup factor.