How do you form the perfect tense in Spanish?

The perfect tense in Spanish can be translated to English as 'I have done/eaten/been'. Firstly, you conjugate the verb 'haber' (to have), which is yo he, tu has, el/ella ha, nos hemos, vos habéis, ellos han. Secondly, you conjugate the verb that you have done. You add the past participle of the infinitive to the stem of this verb, if it is an -AR verb (visitar) you add -ado to the stem, so it would become 'visitado', and if it is an -ER verb (comer) or an -IR verb (vivir), you add -ido, so, 'comido' or 'vivido'.