Many women trying out and looking at laptops in a Walmart.
Women are shopping for computers at a large store.
Women in a Walmart means they are shopping as Walmart  is a shopping mall or a large store, and trying out and looking at laptops means they are shopping for computers as laptops fall under computer category.
Laptops is a rephrasing of computers and Walmart is a specific large store.
Shopping for computers refers to looking at laptops and Walmart is a large store.