In the system tray, you should see a little cloud icon. Click on that and then click on Exit.
ALternatively, you could press the ctrl-shift-esc keys at the same time to bring up the task manager, find verizon cloud, click on it so it is highlighted (you might have to click on the name header to stop it from jumping around), then once it is highlighted hit End Process.
Both of those will stop the app from running so you can uninstall it.
Why do you want to reinstall it?
