To change the default SSID to something unique, you need to access your wireless router administration console. Refer to the owner's manual for your particular wireless router or access point to determine how to access the configuration and administration screen where you can change the default SSID.
For most wireless routers, this is done via a Web browser. Simply type http://192.168.1.1 (Note: the default IP address may vary by vendor, or if you have changed the default IP address, substitute whatever the IP address for your wireless router is).
To gain access to the actual administration console, you will need to enter the administrative username and password for your wireless router. Some vendors allow you to change both the username and the password, while some only allow you to change the password. You definitely should not be using the default username and password since any attacker can find out what that information is from the vendor.
Enter your username and password and press Enter or click OK.