Step 1: Open https://192.168.1.1 in any browser and enter the username and password (By default it is admin, admin respectively)
Step 2: Go To Network Setup>Wireless
Step 3: Disable the WPS, Enter the SSID (Broadcast name of your WiFi) , in Authentication Mode you can select WEP 64bit or WEP 128bit. However 128bit is more secure but have a lengthy passwords. Now enter the password in the provided Key field. Select the key which you want to use.
And match the following settings shown in the picture.
Now your router’s WiFi is secured. The password characteristics of both the authentication type are as follow
WEP 64bit: 5 characters excluding symbols or 10 characters ranging from 0-9,a,b,c,d,e,f
WEP 128bit: 13 characters excluding symbols or 26 characteristics ranging from 0-9,a,b,c,d,e,f.