DB relations in Codeigniter

Hi guys, I'm getting desperate trying to figure out how can I access data from DB by using relations. I have successfully related two tables by setting foreign key and now I am little bit confused.

Let's say I have two tables -> Cars(id, size, color) and Drivers(id, car_id, name).

IDs are primary keys, car_id is foreign key. Now, I'd like to know what color or size is George's car. Could someone tell me what is the easiest way to echo it by Codeigniter?