Do you mean you can't connect via wifi or do you mean you can't log in on the wifi-router to change the settings?

If you can't connect to the wifi network:
- check if the wifi router is on
- check if wifi is enabled on your computer
- Let windows/OSx search for wifi networks and connect to your wifi. Check if the password is correct.

If you can't log in to your router:
- start your web browser
- type in the ip-adress of your router
- login using your password