As a general introduction you might want to look at this post on
Young Learners with some basic ideas.
But speaking generally, you need to plan LOADS of very short activities of just a few minutes each which you can switch around and play with in class. (You can always come back to them after a while, of course.) Also think about the kind of things he's interested in and focus on those; not teaching English per se but talking and working on stuff he's interested in but it just so happens you do it in English.