The present perfect is constructed by using a conjugated form of the irregular verb haber with the past participle.
 

he comido	hemos comido
has comido	habéis comido
ha comido	han comido

The past participle does not change form when it is used in the present perfect tense. For example, Ella ha comido, nosotros hemos comido, ustedes han comido, etc. Like its English counterpart, the present perfect tense is used to refer to the past. In the affirmative, it refers to an action that has already taken place (Elena ha llegado [‘Elena has arrived’]); in the negative, it refers to something that has not happened yet (No ha llegado [‘She hasn’t arrived yet’]).