The Fuel Cell car is a small two person, three wheeled (2 in the front, 1 in the back) car for commuter purposes.
Step 1: Anthropometry and component parts
In literature there is information available about anthropometry in the automotive industry:
The standard J1100 of the Society of Automotive Engineers (SAE) has standardized different dimensions for the space available for driver and passengers in cars: it is difficult to find values for these dimensions in J1100
Automotive Ergonomics (Peacock & Karwowski, 1993): deals with several topics of ergonomics and anthropometry in vehicle design; also has values of important dimensions!
At www.3dcontentcentral.com (a free resource for 3D CAD drawings) there is a car seat model available for SolidWorks. With this model and the data available from literature a new model was made in SolidWorks, the so-called forbidden space model. This is a model with a layout of the seat and the space that is needed to accommodate the driver and passenger: this space can not be used for the structure.
Also in this step you need to have a good idea about all other big componentes in the car and how to accomodate them.
(pictures copied from "Automotive Ergonomics (Peacock & Karwowski, 1993")