This the age of the Internet, you do not have to how to program a PID controller, it has already been done for you. But, you must know how to use the Internet which means a search engine. Oh, you know how to do that. Great. Then use your favorite search engine and search for “Arduino PID library”.
After you have downloaded and installed the library and read the documentation, then you can ask for help. Asking the way you have done is just being lazy.