I'm trying to install Flash Player on my Mac but I keep getting error message: Install Adobe Flash Player wants to make changes. Type your password to allow this. I've entered my user name and password but it won't do anything. Help please?

I've typed in my Username (it automatically shows my first and last name) and I've entered my Adobe password. I've also tried typing in my email address as User name and it still doesn't go through, the box just vibrates. I'm not tech savvy, just trying to download Flash Player.