I am looking for a book explained how to make a computer by using Arm core processors?
Arm don't sell any actual physical processors (well except for some high end development boards). They sell intellectual property, they enable others to build a system on a chip easily with what they are interested in. In the past one could get a processor and some memory and and some other chips and stick them on a circuit board probably with one's own FPGA to do what one wanted. Today most of that can be stuck onto a single chip, instead of a physical chips to stick on a board one licences IP and fits it into a SoC, the board it is put on is there mostly to provide human sized sockets.
Thanks a lot deith