the best time to prune a fruiting tree is when the wounds will heal the fastest. Generally between july 15 and aug 15 (a little sooner maybe depending on how far north you are) Most people don't want to prune then because it is harder to do with all the leaves and for some trees fruit. If it is only 3 years old it should respond just fine to pruning. Rule of thumb never prune more than 25-30% of a tree in any given calendar year. So say you decide by looking you need to take more than 25% off you will need to part of it this year and then finish up the next year about this time. General pruning rules, take out branches that cross or rub against each other, that is take out one or the other. Prune for airflow, take off water shoots (tree too young to have many yet), pick scaffold branches (the ones with the best angle to the trunk the closer to 90% the stronger the "joint" is. If that is as semi dwarf or standard it is going to get very large. The perspective of the picture doesn't let me guess. The hows to prune properly as well as fruit tree shaping is an extensive subject that is hard to answer in a small space. I would start by looking on line for a US extension site that explains open bowl fruit tree pruning and also proper pruning cuts. The explanations of what to prune apply to you just a well. These sites will be marked edu or say extension in them. Cornell, Oregon and maybe Michigan are the ones I would check first. They all deal with a lot of fruit trees in their states and they tend to have great articles. You could also check you local library for books on fruit tree pruning and follow the general guidelines for open bowl pruning. The spacing between branches needs to be enough for good airflow, otherwise down the road the tree could develop any of several problems. Remember, articles and pruning books are full of agricultural words and are one size fits all.