If you want to leave Ijat a tip for writing this Garrys Mod guide you can do so here.
Garrys Mod Walkthrough 10.0 - Building A Working Car (Example)
Garrys Mod 10.0 - Building A Working Car (Example)
Spawn and freeze the object mid-air. This one I called main part.
Spawn wheels (non-functioning)
Use axis tool to attach the wheels to the main part.
Now, it'll be like this.
Now, use thruster tool to move the car. Place three. One for forward/backward, one for right and one for left. For the right, the key is always reversed (e.g. right thruster placed at right wheel -> key is left and vice versa).
Now place the chairs.
Use easy weld to attach is nicely. Tip: Right-click at the bottom of the chair.
Overall view of working car.
Then, use your creativity to make something awesome. Have fun with Garry's Mod! :D