It depends on what version you're upgrading from on how you should do it. Honestly though, what you did should work if you're coming from any version, but uninstalling first is the best way to clean up a few files that have been removed in the most recent version(s). The upgrade guide can always be found at the link below (and in the menu above):
www.sourcecoast.com/extensions/jfbconnect/upgrade-guide
Now, for your issue, if you're getting a white screen, it means there's a PHP error on the page. Please enable error reporting and let us know what the error actually is and we'll help you get to the bottom of it quickly. You can enable error reporting by following the instructions below:
www.sourcecoast.com/extensions/troublesh...ng-joomla-extensions 
Updating
