When a costumer pay using Bank Transactions,  they get a confirmation page with some info "Order SO41" by example, and shows a message of "waiting for payment confirmation", in this view also you can set your bank account information so the costumer will pick one and will make the transaction...

So i need to add a attachment field in this view, so the costumer can upload a payment confirmation, or i would say a "a proof of payment" could be an img, or a document. this document would apper in the attachment files of the SO

i've been trying a lot of things, following old guides but i don't reach it is there any idea how can i get this? what do i need?... 

what i have in my mind is, i need a binary field, in this case the attachment field that already exist just need to inherit, i need a controller that will allow sending the files, and the view, i can deal with the field and the view but i can't build the right controller, can some one give me a hand?