Adding texbox with button on mainpage

Hello
I have question, I need to make website with template with basic view like this (maked in paint 3min ago 😀 )

My problem is with this tex box and sent button. Background I put on website just like picture on main page.In textbox it should be given unique clients number ( something like login, but without password), after click “sent” it should transfer to store (woocommerce).
My question is how to make this textbox, I try copy from some templates, but it’S too hard for me :/ and add this forwarding is totally too much for me 🙁
Theme what I use is a little bit modifited twenty fourteen.

Thanks For help 🙂