Click on the 'Insert' menu at the top of the screen, select 'Formula Field'
Click on the button labelled 'New' when you hover over it.
write in the the formula you wish. If for example your database is called messydbforcars and the field (column) is called cartypes then you would write:
IF {messydbforcars.cartypes} = 1 THEN 'Car type 1' else
IF {messydbforcars.cartypes} = 2 THEN 'Car type 2' else
'No car type'
etc etc - replacing obviously your field name, car descriptions etc.
I would strongly suggest looking at some of the sample reports and guides available to get you used to how to use basic crystal functions.
'J