add custom field to onepage

[BaldevParmar]

hey,

I am new in magento, i need a help for add custom field like delivery instruction, delivery time, contact person, and contact person phone number to onepage in billing and shipping detail. 

thanks in advance,

[talk2tomt]

I am also wanting to add a custom field to the building info, to record additional information. As we host a conference and want additional information.