Entered WEP password incorrectly

In setting up a range extender router/repeater router, on my MacProbook I entered the incorrect WEP password. Password for base router is correct and can access wireless, on ...ext network unable to access do to entering incorrect WEP. Have other deveices connected to ...ext which have the correct WEP and can access that newtwork. How do I correctly set the WEP on my laptop for ...ext network? Running Mountian Lion 10.8.

thanks