you dont , as im sure its a climber , and it will only need a trim after its flowered

yes it is a climber but you can prune it abit when it has finished flowering if you have run out of space.tidy up the shape and remove a few older stems.

We have to prune it three or four times a year in self defense! Fortunately, it doesn't seem to care when or how much we prune, as long as we don't do it from the time it stops growing in fall, 'til the time it blooms.