First things first: you didn't start with a bonsai, you started planting some young plant ( looks like a young spruce) into a container ...
Second, to answer your question, depends on what you want to achieve here. If you want a fat trunk, plant the tree outside, let it grow for a few years, cut back and repeat. If you want movement in the trunk you can apply some wire and make some bends.
In the little container it is in now it will hardly get bigger/ fatter ( it is a common mistake that a young tree planted in a bonsai pot becomes a bonsai. A bonsai pot is the last stage of training a tree and done to slow down growth and or reduce needle/foliage size)