How do I use an imperative?

Imperatives are used to give orders, express encouragement or give advice. They are formed from the present tenses forms of verbs of the second person singular (tu), second person plural (vous) and the first person plural (nous). All you have to do is take the verb form and remove the subject and the final s of any verb which ends in es or as.
Tu:e.g. 'open the box' = 'ouvre la boîte' (notice how it is 'ouvre' without the s)
Vous:e.g. 'leave me alone' = 'laissez-moi seul'
Nous:e.g. 'let's go' = 'allons-y'
There are four verbs with irregular imperative forms: être, avoir, savoir, vouloir. Instead of being formed from the present tense, they are formed from the present subjunctive.
Tu: e.g. 'be happy' = 'sois heureux'e.g. 'please sit down' = 'veuille t'asseoir'(vouloir in the imperative is almost only used to mean please) Vous: e.g. 'know the answer' = 'sachez la réponse'
Nous: e.g. 'let's have this one' = 'ayons celui-là'