This will come naturally if you're also going for the achievement of getting a derelict car to performance level 399.
The first step is to find a derelict. These are hidden cars that you unlock the ability to find after certain quest lines. Refer to the wonderful solution written by NE0182 in One Man's Trash for a full list of locations with videos.
Your derelict is going to start off rather weak. Either buy cards from the tune-up shop or use trade-ins to get at least some cards to give you a decent rating. Then, just win any race.