Before you start using the car sales module you should review and alter the Car Sales default settings.  They are found under the 'Car Sales' tab of the Options screen

Here you can see that we have created a new department (Vehicle Sales) and a new Tax code (Margin Code), we have also created a new account for internal use (ICS - Internal Car Sales).

We can also edit the default purchase questions and set the starting stock identifier and format (i.e. it is possible to use just numbers or add prefixes and suffixes)