Populate fields in a related module

Populate fields in a related module

Hi there

So I have an Account linked to a Contact via a Lookup field. 

As an example, how can I get the address fields that are stored in the Contact to show on the Account record? Surely there is a way of populating this data across, if they are linked?

I need to create a mail merge, which can only be done from one module, and I need the information from two modules.

Please advise urgently.

Thanks