If it is a home WiFi then go to chrome and type 192.168.1.1 and enter then you will see a login page enter "admin" as username (without quotation marks) and again "admin" for password (without quotation marks). See the left panel it have many options click on network and click on WLAN which will be listed under network now you will see password place check the button that says show password in the password text field enter your new password click save on the lower right of the page and you are done Your phone and other device's will get disconnected from the WiFi to connect enter the new password on your phone and other device's