I would prune all of the branches at various lengths, up to two thirds of the way down. Find a suitable node, preferably pointing up or outwards, to help create a bushy tree top, and make a clean cut about a quarter of an inch above it. Use clean cutters, so as to make as healthy a cut as possible.

Optimally, pruning should be done when weather begins to stay above 60 degrees at night. It takes a few weeks to get any new growth, so the sooner you prune, the better the chance to get blooms during summer. Make sure to check the plant daily for any pests, as the new growth will be susceptible to damage. Water regularly, but don't overwater.

Hope it works out for you. =)