在magento中添加签出步骤并将值保存在数据库表中

I followed the steps of this link.

and able to add a step into checkout. I have done some modifications in it and added one step (Character field contact_name) in the checkout after payment.

For that I have created an attribute for sale/order contact_name. How do I save the value into the sales order in magento, So that I can fetch the value of that attribute. Also I want to add some conditions for this attribute like it should be lower case only and does not contain spaces.

The main concern in I want to save the contact name in the database and get the value from the database for it.