If I think what you mean is you are having trouble creating topological entity sets and selecting them, I can explain that. First, at the top, there is a bar that has different selection tools. Click the one that shows one red face and select all of the front wheel. Then press the plus button and create a topological entity set with that, then rename it the front wheel. Then repeat the process for the back wheel and the body of the car.
Hope that helps and have a great day,
Frank Lucci