As Valery Possoz posted in your comment, you can't.
Google Docs works by loading a document from a URL. Localhost is only available to your local computer, not to the outside world. Google can't access your computer and load the document from the localhost URL.
There are some ways you can get around this, like using a Dynamic DNS (
DynDNS for example[
^]). This will require you to install a client on your computer that updates a DNS entry. You then use the dynamic dns name to refer to your computer and the location of your file. This may also require some complicated setup with your router or modem to allow HTTP traffic to pass to the right computer.