Making a vehicle is quite easy.
First you need to determine the number of directions you want your vehicle to be able to look at. The vanilla vehicles use 64, I used 128 to make it look more smooth. Then you render the vehicle in all of those directions and pack it into a spritesheet the game can use.
Create the vehicle entity with all of its parameters, make the item, the recipe and assign it to a technology and boom you done.
If you got any specific questions you can add me on Steam and I will send you my Discord tag.