Customising Twenty Twelve homepage with 3 columns.

Hi,

I’m using the Twenty Twelve theme and have decided to customise it as I cannot find a theme to match my requirements.

I’d like to create 3 box/block columns towards the bottom on my homepage and these two sites show exactly what I need. https://www.ryanlee.com & https://www.chrisducker.com

I am also going to tackle putting a optin/signup form on top of my banner image but that might be another thread? For now I’d just like to create the columns.

I’m new to coding but learn fast and have already created a child theme with style.css and rtl.css files.

my homepage is https://www.carmsalarms.com

So, is this possible and what is my first step?

Thank you.