The easiest way is to simply use Internet Explorer, Edge (for Win10) or Chrome, all of which bundle Flash Player as a built-in component on Win8 and higher, so there's never an installer to download, or an update to install (they're delivered via Windows Update or the Chrome updater, respectively).

For Firefox, you'll need to uncheck the box for McAfee on the download page itself, at which point you'll get the installer that doesn't bundle McAfee. I've posted much longer explanations on the topic, so I'm not going to get into it here, but you're welcome to look through my feed for the longer, more eloquent background.