There used to be a simpler + sign in the Facebook movie collection in your about profile movies section. But no more. They have recently changed it to this;
Simply search for your movie name in the top left-hand search bar. You should see the Movie poster on the right hand side. Click “Facebook” icon under “Profiles” link;
On the main page of the movie, simply click the “thumbs up” icon and afterwards click the three dots at the top-right hand corner of the same movie page to click “SAVE” button. It will be automatically added to your movies selection in your Facebook profile’s about page;
Replace “aatayyab” with your own unique facebook profile ID.