Learn French: Je n'aime pas du tout ce film. - I do not like this film at all.

It adds emphasis. While Je n'aime pas means "I do not like", adding du tout turns it into "I do not like... at all". The phrase pas du tout is a very common fixed expression in French.

Why is it n'aime instead of ne aime?

When the negative word ne is followed by a verb starting with a vowel (like aime), the "e" is dropped and replaced with an apostrophe. This makes it flow better when speaking!

Why use ce for "this"? Could I use cette?

You must use ce because the word film is a masculine singular noun. Cette is used for feminine words (like cette fille for "this girl"). If the masculine word started with a vowel sound, you would use cet instead.

Why does pas du tout come before ce film?

In French, the negative pieces (ne and pas du tout) wrap directly around the verb (aime). You finish the negative "sandwich" first, and then say the thing you do not like (ce film). English puts "at all" at the very end of the sentence, but French keeps it right next to the verb.