How do you form the perfect tense?

To form the perfect tense (which translates in English to 'I have been/eaten/visited') you must first conjugate the verb 'haber'. The correct conjugation for this verb is yo he, tu has, el/ella ha, nos hemos, vos habéis, ellos han. After conjugating this verb then you must add the past participle of the infinitive. This is formed (except in the case of some irregular verbs) by adding -ido to the stem of verbs with an 'er' or 'ir' ending such as 'comer' which becomes 'comido' or -ado to the stem of verbs ending in 'ar', such as visitar, which becomes 'visitado'.