I prove it“Lo” means “it” and comes before the conjugated verb. The verb form changes with tense and mood, as in “lo demostró” (“he/she proved it”) and “lo demuestre” (“I/he/she prove[s] it”).
SP: No tienes que creerme; lo demuestro con hechos.
EN: You don’t have to believe me; I prove it with facts.