how to create wcf web service that has username and password in asp.net?

[soko]

I want to create \[code\]wcf web service\[/code\] that has \[code\]username\[/code\] and \[code\]password\[/code\] in \[code\]asp.net\[/code\].so that by providing that username and password, we can consume any web methods.I have already created wcf web service but i want to add username and password in web service.thanks in advance.