In what language? And what do you want the program to do? Do you want it to accept a number as input and tell you if it’s prime? Or do you want it to start listing prime numbers and continue forever? Or something else…? I suspect that the very first step is to enrol in a school that teaches programming. (This site is not a school and doesn’t teach ‘programming’.) — Tom
I think your toughest obstacle here is coming up with the logic for determining the prime numbers. If you can do that then coding a program in the language of your choice should not be that hard of a task.