Peg110 is correct. In the lower right portion of your screen (when you are typing a reply) you will see three options: Post Reply, Upload a File, and More Options... Click upload a file and then select the picture from your computer's library. Some pics are too big for upload, so you may need to resize it. I typically resize my pics to about 800x400 or something close which still leaves it plenty big to be seen here on the Boards. What I like to do it open the original large pic and resize it to something smaller, and then resave the smaller pic to a different location (I actually created a new folder under My Pictures called "Disboards Pics". This is where I save my smaller pics to upload here.
Why don't you give it a try on this thread, just post a pic of anything, and we'll see if we can't help tweak the process for you.