are there certain times of the year when you should not plant this tree or will it be ok now to plant ? thanks

you dont say if you have already purchased the tree yet. if you have here is what you do .soak the tree roots in water. dig the hole and take some of the soil mix this with farm your manure that can be purchased from a garden centre and then mix in a hand full of bone meal. after planting the tree with this mixture firm the soil arround the tree and again water.for the next month unless very wet weather pesists you must water the tree every day . on the best time to plant a tree.
the autunm is the correct time to plant trees, once the trees have dropped their leaves(deciduous trees) follow the same instructions as above but you do not have to do the watering part.