You need to sign up at another web page that lets you upload your pictures to it. It then gives you links that you just copy and paste here. Image hosting, free photo sharing & video sharing at Photobucket is a popular one.
When you want to upload pics, you post whatever and then click Go Advanced rather than Post Quick Reply which will take you to a page where you can upload your pics.
TinyPic - Free Image Hosting, Photo Sharing & Video Hosting is free site that doesn't require an account. you just upload and copy the IMG code and paste into the textbox.
took this picture today, while blazing in my home town in down east maine, in my car. this is just a little side road near a bridge that clammers usually park at for low tide. gorgeous day to be high