In french, how do you conjugate past and future tense?

If you are talking about future simple then you use the conjugated version of aller and ther put the infinitive of the verb that explains the action, to contextualize: I am going to eat: Je vais manger. 

Passé compose is using the conjugated form of avoir (or etre if it is a vandertramp verb) and then the past participle of intended verb. for example: I ate: J'ai Mangé or as a vandertramp: I went: je suis allé(e) 

Another way to use the future tense is to use the avoir endings with the verb you want to conjugate. For example, I will work would be written as Je travaillerai. 
"We will work" becomes "Nous travaillerons."  and so on. For verbs that have an "re" ending, we drop the "e" before adding the avoir ending.
Ex. "boire" I will drink ~> Je boirai.
Like all french words, there are exceptions, and these exceptions have stems:
 Avoir - aur
 Etre - ser
 Faire - fer
 Aller - ir
pouvoir - pourr
vouloir - voudr 
venir - viendre