To move your model, press on it using only 1 finger. Drag your finger across your screen to move it in the real World.
If you want to bring it forward or backward, you will need to click and hold your model while physically moving in your environment. Let go of the model when you are satisfied with the position
Often times, your model will be composed of multiple parts that can be selected. This allows to highlight these parts when presenting your World to others and also triggers the annotation if there is one attached to your part.