Cook couscous according to package directions and set aside to cool. Chop and cook yam and chill (see below). Chop apple and nuts. In a seperate bowl combine vinaigrette, honey and mint; set aside. Mix couscous, fruit and nuts together. Pour vinaigrette mixture over and toss to coat well. You may not need all the vinaigrette.
Note: If you have not had cold yams, they have an amazing flavor. I love them in salads of all kinds. I have found the easiest way to cook them for this use is to dice/chop them to the desired size and then place them in a dish with a little water and microwave them until they are tender. Drain as soon as finished cooking and chill. I would recommend this preparation for this, as it is fast and easy and you can do it earlier.