Blueprint Help Car Configurator Paint Material Slot

Hi guys, currently working on my own car configurator using the template from the UE4 A5 configurator sample: Exploring the New Real-Time Car Configurator Sample | Unreal Engine Webinar - YouTube, in this video at 49:57, he states that he’s added in that material slot to the blueprint but doesn’t show how that is done.

Is anyone able to show me how to create a material slot within a blueprint to appear in the details panel so that I can use his method for the variant paint switch.

an example of my details panel compared to his:


As you can see he has the paint material slot in his whereas I’m not sure how to achieve that in mine.

Any help would be greatly appreciated.

Thanks in advance.