There's a really short tutorial that explains image planes in detail in the free section, if you download this one it will give you a visual which is probably easier to understand https://simply3dworld.com/movie_pages...html?tut_id=64

Another tutorial that's quite fun and helpful if you're a newbie is the cartoon dog, it's got image plane set up as well https://simply3dworld.com/movie_pages...html?tut_id=87

There done in older versions, but too much hasn't changed in the modeling field so it should be easy to follow.