So is "farlo" equals to "lo fare" or is one of them used more commonly? please clarify thanks.
«lo fare» is not used often. It is better to attach the pronoun to the end when the verb is in the infinitive or in any of the imperative conjugations.
You mean how the pronoun attaches to the infinitive of «farlo»? Then, yes. Pronouns can only attach to the ends of verbs in the infinitive and in the imperative, just like in Spanish.