how do I analyse a movie?

start by looking at the basics: plot, characters, themes, and visuals. take notes on how they connect and what emotions they evoke. also, don't forget to think about the director's intent and the context of the film; that can add a lot to your overall understanding.

Ask yourself questions about the film? Millions of examples that can be interesting but just to pick one, note that the opening and closing shots or scenes often have special significance. What is the relation between the two? Do they suggest some kind of arc or shift or continuity of theme? Why did the filmmaker choose those particular moments to begin and end the film?

Do you mean professionally? Like looking at the plot structure and narrative technique and what not? Or for your own enjoyment? Because that might start with doing more than just consuming a movie, but reading between the lines and thinking about character motivations, extrapolating their possible background from hints the writer and director may have planted without saying "that guys had a tyrant mother" or "that character is homosexual". You'll have to think and look at what the tale you are told does to and for you, how it connects with your life.

There's a hundred different ways to watch a movie just like there's a hundred different ways to read a book. Think of it like a hiking trail through a forest: Different people taking the same path will notice different things. A birdwatcher will mostly look up in the trees and listen to birdsong. Someone who likes to forage mushrooms will look on the ground. A hunter will look for droppings and markings. Young lovers will look for a secluded spot to spend some time together. And so on and so forth. There's lots to be said about each and every one of these aspects. The most important question right now is: What aspect of movies are the ones you like think about most? There's costumes and makeup, stunts, technical aspects of filming and editing, story structure and writing, acting,...