...
Your theme is now ready to be installed.
You have to either do a ant run-install-file or import the file your modified /themes/mytheme/data/ThemeData.xml through the webtools.
If you went the route of /framework/common/data/CommonTypeData.xml then you must do the same with that file as well.
How to use it
If you did a backend theme, then select it through the themes link at the top of any page (maybe in preferences for some themes)
If you did an eCommerce theme, then select it in the Product Store associated with the Website you want to use it on.
If you want to upload your theme to the Visual Theme Gallery, simply create a mytheme.zip file from the /themes/mytheme folder and upload to the gallery.
...