flush DNS cache on mac 10.6.8 w/o admin. password

I'm trying to access a site but they say they're server has changed and that I have to flush DNS cache first. I have a Mac 10.6.8 and when I go to applications, utilities and terminal I'm unable to get past the code because I don't remember my administrator's password. How do you reset the password so I can do this or is there something else that can be done?