Change Site Layout

Hello,

I am totally new to wordpress and having a little trouble understanding the concept. I want to create a website which is similar to this one: https://sdedsynergy.org

I am especially interested in creating the same navigation structure. I know how to create new sites and modify them on a basic level, but I dont know how I should create those little preview views. This is the template I am using: https://www.ads-software.com/themes/radiate

Thanks for your help!!