Uninstall normally, and reply YES to the question "Do you want to remove the Addon Manager" ?
However, while this will remove the whole software from the sim, it's not really a "clean" installation, because this will still leave all your settings untouched.
Which is of course correct, since the preferences folder contains all your custom airport customizations, your custom pushbacks, possibly custom liveries and all your custom airplane preference that you might have spent time working.
If you think you have a problem which require a "clean" installation and you suspect it might be caused by some of your custom profiles, removing even the %APPDATA%\Virtuali folder would remove everything, including all your customization so, that's what we might call a "clean" installation.
But perhaps, before doing that, it would be best if you just asked why you think you need a clean install to begin with.
