Getting around on foot is practically impossible, so you will soon learn how to use a car to go to carry out the assignment assigned by the fixer or simply explore. The first V car is rather "normal"; in Cyberpunk you can get your hands on the wheel of many other models, some truly futuristic and highly technological. How to change cars, then?
The quickest and easiest way is to steal one. However, this involves breaking the law, and the Night City police are not known for being lenient towards criminals (although crime shows no sign of abating in the city of dreams). Also, to steal a car you will have to meet a certain requirement of physical strength (Physical 6): it is certainly not GTA, it takes the muscles to get someone out of the seat of a car!
To avoid all this , you could get hold of Eurodollars and buy your own. It is necessary to finish the first act of the game, by completing the mission "The Heist", to be more free to explore Night City and thus be able to change cars.
You will receive a message on V's phone, from by a fixer: exploring an area of the city and completing missions you will be contacted by the local fixer who will inform you of the availability of a new vehicle. At this point, all you have to do is make sure you have enough credits to purchase it. The new car will be displayed on the map and also in the mission log, allowing you to find it at any time.
One of the best things to do with your new car is to drive through the streets of Night City with the right music: on the vehicles you can listen to different radio stations, you will surely find the one that suits your style.