No. This isn't possible in this version of the game. The game doesn't have a Free to play option. If you want to drive a truck and a trailer, you need to start / load a game and purchase them. In Showroom, the developer presents the available trucks and trailers that are available in the game. There is no way to select a combination and use it from the start of the game. If you still can figure out what to do, use Google or Youtube to find tutorials about the game.