Depends on what form you want it to take. Ours we keep as a bush, so it is quite severely pruned in winter to keep it within bounds. Did it with a chain saw last year as the main trunk is now about a foot across and we wanted to really reduce it in size. Otherwise you can leave it alone to grow as it chooses. If you do prune then when it is dormant is best, ie. Winter.

thanks for your answer big help :)