On the top menu, select Extensions >> Extension Manager
Click on the Manage tab, filter by templates and search for RSDinah! and RSTemplate!, select the results and click on Uninstall (the image below only shoes results for RSDinah!).
If uninstallation was successful, you should see this message:
The installation of any template, component, plugin or module is done strictly using the Joomla installer, as the above example illustrates.
