How do i cite my essay?

I am writring a persuasive final paper and the only thing i haven't figured out is how to cite my essay... i found statistics and things i want to *** into my essay but i am unsure as to how i avoid plagarism and etc. Do i just add the websites used at the end of my paper of does it literally have to be right after each statistic i have to include the site i used?? HELP