Hi there,
It's not possible to connect to the external hard drive wirelessly but there is a method which requires you to have another computer or laptop within the house which is the same Operating System as the one you want to connect wirelessly, preferably Windows. It also has to be connected to a router, which you too are connected to. If your using a laptop, you must be able to connect to the router wirelessly.
1. You must connect the external hard drive to the desktop, or another laptop.
2. Connect the computer to the router, and set it up using the "Network Wizard". Then right click the external hard drive on "My computer" and click the "Sharing" tab and turn on sharing. Also, tick "Allow network users to modify files" to allow you to change, delete, edit or create files when connected wirelessly.
3. Connect your laptop to the router wirelessly. This should then detect all network computers and you will then be able to view the files and shared hard drive.
That should do the trick, also you must always leave the computer which the external hard drive is connected on at all times to use it.