How to populate data from one field to another on a different page

My sales team is using Sales Quotation and is requiring the team to complete the Request Receipt Date field before the quote can be sent. They wanted the same field on Business Opportunity (custom field created) to feed this native field. If the salesperson forgot to input a date on the BusOp, they would still be able to on the Request Receipt Date on the Sales Quotation. I have been unable to figure out how to have the field on the Sales Quotation populate with the date entered on my custom field on the BusOp. Does anyone know how to accomplish this?