How to form the perfect tense?

The perfect tense is formed with the present tense form of haber plus a past participle. The present tense forms of haber are: (yo) he, (tú) has, (él/ella) ha, (nosotros) hemos, (vosotros) habéis, (ellos/ellas) han. A past participle of a regular verb is formed by dropping the infinitive ending and adding: -ado (for -ar verbs), -ido (for -er and -ir verbs). E.g, the past participle for comer is 'comido'. Putting this together, we have 'nosotros hemos comido' which translates to 'we have eaten'.