To form the tense you use the following structure:

HABER +

The parts of HABER in the present are:

he / / ha / / / han

The past participle is formed by adding to the stem of ar verbs, and by adding to the stem of er and verbs. Both parts are then put together.

Por ejemplo:

yo he (tomar)
tú has (comer)
hemos vivido (vivir)

Irregular past participles include the following:

abrir >
> dicho
escribir >
> puesto
hacer >
romper >
ver >
> vuelto