internship is a required part of the degree.
you go classes for 3-5 years
then 1 year of internship
then you get your phd or psyd depending on your program
however, you can't jsut see patients once you get your doctorate. the state you are living in requires a license for the practice of psychology. To get a license you have to be supervised by someone for 1-2 years. This is called the post doc year(s). So you have another hoop to jump through and find someone who will supervise you in your area (geographical or speciality). there are informal ones that are more like a supervised job and formal ones that are more like an internship with structured learning. Some specialties require the latter (e.g., neuro). so then you complete your post doc, take the national test called the Examination for the Practice of Professional Psychology (EPPP for the cool kids), and maybe take oral exams from your state. then you are licensed and can see patients independently.