well you need to upload the picture to somewhere to host it... facebook, imageshack, photobucket, ect... then grab the image url. It will look something like http://someplace/photo.jpg
often you can right-click the uploaded image and "copy image URL" then on this board you click the little icon in the reply box that looks like mountians... It will say "insert image" when you mouse over it. When you click it a box will pop up asking you to enter the URL of the image. paste the URL you copied before into that box and click ok and it should work.