Can you give me some tips about how I can write a synopsis of the movie The Crucible?

A synopsis should cover the main elements of the movie. You can use headings to separate out these different elements and create a clear structure for your paper. One possible way to organize this would be:
Introduction. This should discuss the author Arthur Miller, and the political background of the McCarthy era. It should introduce the purpose of the play and the main points Miller was making about mass hysteria. 
Setting: This section should give information about the period in which the play was set and the degree to which it provides an historically accurate portrait of the Salem witch trials.
Characters: You should include short descriptions of the main characters including John and Elizabeth Proctor, Tituba, Abigail Williams, Mary Warren, Rebecca Nurse, and John Hale.
Plot: In your description of the plot, you should describe the main events of the play in chronological order. You might start with Abigail's affair with John Proctor and then move through the various witchcraft accusations and Proctor's final refusal to submit a signed confession.
https://www.newyorker.com/magazine/1996/10/21/why-i-wrote-the-crucible