Changing homepage template to add more promo fields

Daniela Ogden 2

I want to change my current homepage template to include an additional row of three promos (test and image). How do I do this when my template only includes Promo 1, Promo 2, Promo 3?

This is the page I want to change:

http://www.edgewood.org/

I want it to look like this: