There's a free, high quality, wiring demo on Etsy by Colin Lewis, you have to sign up, but it is free once you register, the url was posted in several recent threads. Watch the tutorial, try to do it on a couple random branches you cut off a tree in the landscape. After that, you can look at your Thuja again, you will know what to do. I applaud your enthusiasm.
Thuja, are North American native cousins of the Hinoki cypress, Chamaecyparis obtusa. Most everything written about Hinoki is more or less true for Thuja. This includes that they are very reluctant to back bud. Once a stem is old enough to develop brown bark, once it is no longer green, it will not produce any new active growth , no buds that will suddenly grow on a stem once it turns brown. This makes Hinoki and Thuja a difficult tree for someone new to this hobby. But both are lovely as bonsai, and are really good species to learn how to grow and control.
You tree is young, it needs a much larger diameter trunk to look tree like. I would just leave it as it is (it would be okay to rewire it once you finish the Colin Lewis tutorial). Don't prune anything else off. Get it back outside now for the winter. Thuja is very cold hardy. In spring, the goal will be to keep it growing. Sun and fertilizer will be all you need to do until late June or early July. It is very important to keep any little sprouts that appear along the trunk. These will become the future branches of your bonsai. It is a nice cultivar of Thuja you picked to work with.
