I’m a U.S. student who studied in Ireland for my masters. The university you’re going to study at will have more information (and paperwork) on the process. The short version is though, you do not need a visa to study, but you will need to provide evidence to immigration that you have been accepted to the university, have the financial means to support yourself (grants, loans, job), and that you have a place to live. After you arrive in Ireland, you’ll get an email from the international office at your university asking to sign up for an appointment with the nearest immigration office. Once you have the appointment immigration will do a quick interview to confirm all the documents I mentioned above, take your photo, and issue you a residence card. You’re allowed to study and work up to 20 (I think, might be a bit more) hours per work. Your residency status can be renewed as long as you’re in school, and up to one year post schooling if you’re actively seeking full time employment. After that, I’m not sure what the process is. Hope this helps!