Yes, you can install a new version on top of the previous one. I.e. you don't need to uninstall the previous version. However, you do need to
exit the application before beginning the installation.
To exit NetWorx, click its icon in the notification area and then click
Exit in the popup menu. (Clicking the cross button in NetWorx interface only closes the window, it doesn't exit the application - that's why you need to use the Exit menu.)