How to populate a Form with data from different Tables

Please could someone suggest what is the easiest way to populate a Form with data from different Tables?

In my relationships, the main Table is CONTRACT which is linked to the following Tables:-
OWNER
PROPERTY
RENTER
RENTAL INCOME

There is a ComboBox on my RENTAL INCOME FORM to choose a Contract ID.
When the Contract ID is chosen, I want the RENTAL INCOME FORM to automatically show the following information:-

CONTRACT TABLE (start date, end date, rental amount)
OWNER TABLE (owner ID, owner name, address, phone number)
PROPERTY (property ID, address etc)
RENTER (renter ID, name, phone number)