Fix Header and Out of Stock for Shopify Store

I have a Shopify store and I need someone to build in this code for me so I can email customers when the product is back in stock. I have the code, I just need someone to do it for me. I also need help with the theme that I have, I need the header to stay in place and the main logo to only stay in the home page. - Out of Stock email notification - Keep header in place - Main logo only on homepage