Whenever I try to download flash, it says that I need to close chrome even though it's closed. What should I do?
[moderator: edited title to accurately reflect issue being reported]
It's possible Chrome, or some other application identifying itself as Chrome is still running in the background. Use Task Manager (Windows) or Activity Manager (macOS) to see what 'Chrome' program is still running and then terminate it.
Note, however, that Google embeds Flash Player in Chrome and there is no need to install it separately. Chrome does disable Flash by default and you most likely just need to enable it. See Use or fix Flash audio & video - Computer - Google Chrome Help troubleshooting steps.
If you're using any Chrome apps like Hangouts, they keep Chrome running in the background all the time. You'll need to exit those, too.