Finding a parking space on campus isn't that difficult, but you'll probably have a bit of a hike to get there from your dorm or classroom. All of the student-accessible lots are on the outskirts of campus-no one can bring cars into the main part of campus without a special permit from university police, and these only last for about an hour at a time. This can make it more difficult to haul groceries or move other things between car and dorm, but generally that's not a problem for students.
Unless you absolutely loathe walking to your car, you won't have to send your roommate outside with a lawn chair to save you a good spot. If you really are worried about it, however, you might do just that-some such incidents have been known to occur. Thankfully, though, students hardly ever have to leave the Notre Dame environment. You won't have to trek to a parking space far away often, but when you do, it's never much more than a 10-minute walk away.