How can i change my linksis wifi password

If you forgot your login and password , you can hold down the reset button for 90seconds and it will reset everything, but you will have to reconfigure your router.
Linksys's default login/password is admin
Some older routers only required the password admin to be entered , others required login and password to use admin in both fields

Here is the user guide.
Page 20 has password info
http://ec1.images-amazon.com/media/i3d/01/A/man-migrate/MANUAL000000300.pdf

access the GUI if it still on the default settings otherwise press the reset button at the back