Slide Master

Go to the VIEW toolbar and click on Slide Master...

This opens the templates for the slides. Your slides are still there, don’t worry!

Make sure you are on the top/parent layout on the left, the one with "1" beside it...

• Select all the text inside the title box (below left), OR
• Select the title box by clicking on the edge (below right)

Go to the Home tab...

• change the font type to one of the fonts shown below.
• pump up the size to 60
• click on B so it's not bold.  

With the heading text still selected, go to the SHAPE FORMAT tab and add a style under Quick Styles. 

What you'll notice is the headings for all the slide layouts are now that font type and style...