First, you need to prepare the following devices:
- A DSL/cable modem for your Internet connection
- An Ethernet router connected to the DSL/cable modem
- A computer connected to the router
- Your Mini connected to the router
- A USB hard drive connected to your Mini
Then, you need to connect them together. The following diagram shows how, sans the hard drive.
For more details, refer to the Quick Start Guide, Connecting Mini section. (downloadable from here)