As it already has 4 branches growing outwards…Sounds like a "shrub" is what you may have. I'd love to see a picture of it…But without that, I'd say…Start pruning (pinching) from the top, down. Creating a "fuller" "shrub"…The "pinching", or 'pruning' back of each of these four, will increase the 'bushiness' of a shrub.
