Help me out! My doors dont work!

I just started minecraft yesterday. I am trying to make a fancier house, but for some reason when I make a door, it wont attach. Am I doing something wrong? Does anyone have any ideas how to fix it? I want to make a stone house because creepers blew up half of my log cabin. Do I need to make a metal door for stone houses?

Any help is appreciated!

EDIT: Shine_on taught me what I was doing wrong. Thank you so much for the help guys! This game is so much fun!