[Phantom Lord]

You can't. It has to be on a server to be accessed.

[A.A. Cunningham]

HTML bootcamp

[Hanging Chad]

"...But how can I post a picture which is saved on my computer and have it appear in the post?..."
- -
You can't.

[Liberal Classic]

The picture you want to post has to be on a website, not just on your computer.

If you know some HTML you write the code for an image like so:

<IMG SRC="http://www.freerepublic.com/images/frlogo.gif">

This produces the image in the web browser:

[martin_fierro]

If you have what's called a "static IP address" and a nice, fat upload pipeline to the internet, you can serve the image up directly from your computer.

But if you're a typical broadband user (with a NON-static IP and comparatively tiny upload pipe), it's more practical to post the image to a server better suited to that purpose.