Step 1 : Open http://192.168.1.1 and login using your username and password [By default both the username and password is admin.It is recommended that you change the default username and password to secure your router’s configuration page].
Step 2 : Now go to Wireless settings and under Basic configuration, enter a SSID (SSID is the name of your network), then select your country and enter the Max clients that can connect to this wireless network. Now click on Apply/Save button.
Step 4: Now enable WEP Encryption.
Step 5: After that Set Encryption strength to 64 bit or 128 bit (128 bit encryption requires longer password but it is more secure).
Step 6: Select Current Network key to 1 and in the Network Key 1 text field, enter the password that you want set for your Wi-Fi network.
You can also setup multiple access point on your modem, you have to just enable Guest/Virtual Access Point in the Wireless Basic Settings. If you have to filter devices from your network, then you can use the MAC Filter option under Wireless Settings.