This means changing the verb into a different form. In Spanish, it isn't usually necessary to use the subject pronoun (I/you/he/she/it etc). The verb ending makes it clear who is doing the action.

So, if you wanted to say: ‘You have been to the hairdresser,' 'she has eaten all the biscuits’ or anything ... you need the correct person of the verb haber (to have) plus the past participle.