chelseakissinger is correct, however I'd like to add that there is also what's called the "imperative tense" in French. You use this to command people to do (or don't do) something, which is probably what you had in mind.

You can say something like "You don't eat pie," which is "Tu ne manges pas la tarte."

tu = you
ne ... pas = don't
manges = eat
la tarte = the pie

But you can also say "Don't eat that pie!" which is "Ne mange pas cette tarte!"

ne ... pas = don't
mange = eat
cette = that
tarte = pie

See how "mange" and "manges" both refer to the same person, but that it changes when the speaker wants to switch tactics. It's like when "am" changes to "was," depending on what time you're talking about. There are seventeen French verb tenses total (compared to twelve in English).

You can read more about l'impératif here: http://french.about.com/od/grammar/a/imperative.htm

I recommend this dictionary, verb conjugator and forum (all through WordReference.com):

http://www.wordreference.com/enfr/
http://www.wordreference.com/conj/FRverbs.asp
http://forum.wordreference.com/forumdisplay.php?f=25

basically you put "ne" and "pas" around the verb.

I don't eat apples--Je ne mange pas les pommes.
You don't like the color green.--Tu n'aimes pas le couleur verte.

Just Dont you will say "Ne faites pas" or "Ne pais farire" mainly it depends on the context of your sentence. This is what I recall from my studies of the language