Apple pruning - duo trees

[olrose]

I am thinking about planting an apple tree with my kids. I have spotted a duo apple tree that has a cooking apple and an eating apple on it - www.pricedropdonkey.com/cheap-food-drink/fresh-food-deals

How do I prune this tree. I have read about pruning apple trees and it has gone over my head, even though I have read the article a few times. Does anyone know how to do this and can explain it, in short and in terms that I can understand?

These are tiny patio trees, so they should be easy to keep in control. I doubt you'll need to do anything more than maintenance pruning: keeping it in a nice open bowl shape and removing any branches or twigs that are crossing to avoid disease.

The main thing is to remove any branches that direct themselves back to the middle of the tree. Shape wise, think of a diamond, narrow at the bottom, fat in the middle and narrow at the top.