How can I display descriptive text with a PowerPoint template thumbnail?

[NorthernLight57]

When creating a new file based on one of the templates available to download from Microsoft, you can click the thumbnail and see a picture of the title slide and some descriptive text explaining the purpose of the template. I'd like to know how I can replicate this effect with templates I design for colleagues. Does anyone know how I can achieve this? I'm using PowerPoint 2013.