Wow, when I saw your E-Mail that said you weren't getting an answer on the support forums, I had assumed you had given it a little time. Just to be clear, calling me on my cell phone for support is really only acceptable for paying clients. Also, contacting anyone directly on an issue you posted only a couple hours ago is also not acceptable.
Having said that, everything you need to know is right in the documentation: http://codex.wordpress.org/Inserting_Images_into_Posts_and_Pages
The Link To settings determine the URL/web address to which the image will be linked when clicked on by a visitor to your site. You can specify the following image link settings:
- Attachment Page: Links your inserted image to its WordPress media attachment page.
- Media File: Links your inserted image directly to the original, full-size version of the file.
- Custom URL: Allows you to set a custom link URL for your inserted image to link to when clicked.
- None: This setting will remove the link completely, rendering the image “un-clickable”.