請問如何在notebook 設定安全性的無線網路呢?

You need to go to your router's admin screen to setup a password first by selecting some kind of encryption protocol, such as WEP.

Than, enter your password in your notebook accordingly when the wireless connection prompt you for the password.

For how to setup a password in your router, you need to read your router's user guide. If you don't have a hard copy, go to the router's website and download one.