If you're trying to install DesignStudio included templates - please refer to mExtension.
If you've purchased a template as one-time paymnet:
After installing the template via mInstaller, you should be able to find the project's components in FCP at the following locations:
the main Template - in the Generators Browser, under the motionVFX category,
the Title and the Lower3rd - in the Titles Browser, under the motionVFX category,
the Transition - in the Transitions Browser, under the motionVFX category.