How to relate to the building polygon data from Open OS data?

I downloaded the attribute data in CSV format, which contains fields including building_id and ref_toid. However, none of them relates to the ID of the building polygon data from Open OS data.

https://www.ordnancesurvey.co.uk/opendatadownload/products.html

Just wondering if you know any way to relate your building attribute data to the Open OS spatial data?

Many thanks.