1. Just type http://192.168.254.254 on your browser.
Then click login.
2. Go Wireless tab then click on Security.
On this menu you can see option for SSID (Wifi name), you change it if you want. You can also enable or disable your wireless name by clicking the button. Security mode is also found here where you can set options like WEP, WPA and WPA2 encryption.
3. On the Pre-Shared Key field type your desire Wifi password then click Apply. Allows 8-63 characters.
Hope this helps.
That procedure is outdated. If you're LTE subscriber, normally you would have to go to this site 192.168.254.254 to go to the modem's page. Then login using the username and password which is admin and @l03e1t3 respectively.