You need to upload it boy!
Some sites out there will let you upload and picture and "hot link it" (post that picture from their server on another page, such as this forum) but there are few. Your best bet is to go into the members image storage on this very forum and upload it there. Than it's really simple. (After you have uploaded it) Right click on the picture and choose properties. You will see a URL in the pop up window, copy that. Go to post a reply/new thread and then in the message box do the following.
Press the Img button right above the text box.
Paste the URL
press the Img button again. Should look something like this [ img ]
http://www.mortystwistedworld.com/picture2.jpeg [ / img ] only without the spaces.