PowerPoint: Applying a New Template to a Saved and Current Presentation

Download and save the new template locally on your VDI
Open current presentation in PowerPoint
Select the View tab, then click the Slide Master command.
The presentation will switch to Slide Master view, and the Slide Master tab will be selected on the Ribbon.
In the left navigation pane, scroll up and select the first slide
Select the Themes in the Slide Master view
Click Browse for Themes
Navigate to the location of the new template
Select new template and click Apply
Click Close Master View
Save the Presentation