It depends on what device you are using to look at this forum. If you uploaded your picture to a computer you first have to upload the image to a photo website such as "Photobucket", "Flickr", "Imageshack". Then copy the picture link the website gives you. Then you paste the link in between the [ img][/img ]code on this forum and it should work.
If you are using and Ipad or Iphone device it will be a little easier for you. You can just take a photo of you screen by pushing the home button and power button at the same time on your device. Then you can use this free app Uploadr on the app store https://itunes.apple.com/us/app/uploadr/id352668953, choose you image. It will then automatically give you a link. All you have to do now is paste the link between these [ img][/img ] on the forum and your done.