Design

On the DESIGN tab and use the drop-down menu to choose the theme...

Browse for themes...

Expand This PC if it's collapsed...

Then click on your Z: folder in the list, and double-click on the COMP 6 folder to go into it.

Double-click on the PPT Theme - Quotable file to load it.

When you apply it, your first slide will look like this...

You can keep the green theme or choose other colors. Go to the drop-down menu for Variants...

...and go to Colors>.. and hover over the list until you find one you like.