you have to build a research facility and a factory hall, then get some inquiries for parts in your storehouse. you'll need an engine, a chassis and a body (all for one size).
in the left corner of your research facility is a drawer, the 1st drawer is marked "prototypes". here you are able to design new cars by selecting the apropriate parts. when you've done that, your engineer will probably give some hints how to improve the car.
back on the factory grounds right click and select "new production" from the menu. select the factory hall and another guy will appear who asks which car should be built and how the factory should be installed. your only choice is "manual1" here. after that it takes some days to install the needed machines, time enough to order parts and hire some workers (you'll need 80 skilled workers to get your production at 100% capacity usage).
go back to your factory and assign the workers to the production. the information screen shows details about the production's costs and effectivity.
hope i could help. have fun with the game!
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