The documentation says
Open up the process management console: http://localhost:8080/jbpm-console Log in, using "krisv" / "krisv" as username / password.
however krisv is .... not a good person, how to log into jBPM5?
What do you mean, I'm not a good person? ;)
If you use the installer, that is one of the users that is configured by default. You can add your own users by editing the users.properties files and roles.properties files in jbpm-installer/auth (like here) and rerun the installer. They are copied to jbpm-installer/jboss-*/server/default/conf and specify login information for your application.