I cannot uninstall flash player, please help

Hi, I cannot install flash player in my mac book pro. When I clicked uninstall botton from Adobe flash uninstaller( which is already download in my Mac), there is a small box pop up"Adobe Flash Player Uninstaller is trying to install a new helper tool", then ask me  to enter User name and passowrd, on the right coner of the box, there is cancel or install helper icon, I tried many time of the password, it doesn't work and I cannot uninstall the flash player. 

could you please help me because i tried to do these thousand times already!

Thank you! 

Rui