Custom product field

I found some code on the woocommerce website that explains how to add an extra field to the billing step. The code for how to add that field to an order email is also provided.

What I can´t seem to find is, how to migrate this proces to the product page.

I´d like to give the use some extra fields on the product page, and I want to be able to read out these fields in the order page.

Does anyone know how to do this?

http://ww.wp.xz.cn/extend/plugins/woocommerce/