Uninstall

To uninstall properly, follow the  “Uninstall or remove apps and programs” section in this document :

https://support.microsoft.com/en-us/help/4028054/windows-10-repair-or-remove-programs

You don’t need to uninstall the 32 bits version before installing the 64 version, but you will not able to start the 2 version at the same time.