How do I form the conditional tense?

Take the infinitive of the verb (parler) as with the future tense and add the endings for the imperfect tense e.g 

Je parlerais, Tu parlerais, Il parlerait, Nous parlerions,Vous parleriez, Ils parlaient 

There are some irregular verbs such as avoir and aller which change their stem and will need to be learned as exceptions to the rule.