Animal shelters - please help, I am like little baby.

I promise I've looked around for answers, but I'm kind of a noob and I'm missing foundational info.

So livestock need a "shelter" - ok, got it. Four pillars and a roof will do it.

How do I make this?
Do I have to make a staircase to make a roof?
Please help. I need a roof and it's raining.