Wanting to delete Amazon WorkDocs Drive

There's an app that I downloaded by accident called Amazon WorkDocs Drive. The app always opens up automatically on my computer and there is only an option for me to minimize the pop-up, not exit out of it completely. It's driving me bonkers and I'd like to uninstall the app but I can't, because I keep getting an error message saying that the app is open.

I've tried restarting my computer several times now and don't select the "re-open windows" option, but the app still opens automatically. Any suggestions on how I can uninstall this app?