After downloading the software, double-click the .exe file and follow the installation wizard. You will be prompted for admin rights if you don't have enough rights to install a software.
To uninstall WinTask x64, go to Start/Programs/WinTask x64 and click Uninstall WinTask x64. Follow the uninstall wizard.
When you uninstall WinTask x64, any scripts you have created are not deleted except if you have checked the Delete scripts directory checkbox in the uninstall wizard last screen.