I started a project in VTSCADALight, but had to get a license due to the tag count. How do I activate the license on an existing installation? Couldn't find this anywhere in the software or the help files.

You reinstall.

I have actually called support over this.

Reinstalling the software really is the best approach, it gives you the latest version of the software and automatically updates your apps for that version. It really doesn't take that long either.