Copying Data from one field to another

Copying Data from one field to another

Hi guys,

Sorry, I know this type of question has been asked a million times before but I am completely new to writing the scripts for custom functions and I cannot figure this out.

I have a custom field 'suburb' in both the lead and contact module, as in Australia we don't really use the term city for a locality. However, I cannot get this suburb field to integrate into the 'location' box on a meeting. So to get around this I want to automatically copy the data in the 'suburb' field of a lead into the 'city' field (which is the system-defined line that will appear in the meeting location).

I will execute this via a workflow when the suburb field is edited. 

How do I write this code?

Thanks in advance