Ok heres I hope what will be a step by step on posting a picture.
step 1: go to http://imageshack.us/
screen should look like this:
Step 2: click the "BROWSE" button
Screen should look like this:
Find where your picture is stored on your computer and click on it once.That window should then close automatically.
Then click the host it button.
Wait a few seconds to about a minute (depending on internet connection type).For the picture to load.
The screen should look like this: