Switch major from civil engineering to computer engineering

What is the process to switch majors and how hard/easy it is?

Since you are transferring within the college of engineering and computer engineering is not an impacted major, its as easy as filling out a form with the College of Engineering’s dean’s office. I wouldn’t recommend trying to switch immediately if Fall 2017 will be your first quarter at Davis unless you are 110% sure that is what you want to do.
I would however recommend you try to get into EEC 1 which is the intro to the ECE department class, its typically only offered fall quarter and you’ll have to take it eventually if you want to graduate with a computer engineering degree. It will basically give you an idea of what the computer engineering classes cover and if it is something you actually want to do.