The Past Participles in Spanish can be used in a variety of ways.
First we saw them used in the Present Perfect Tense with the verb Haber
Has -ar = -ado (hablar = hablado)
Ha + Past Particple -er = -ido (comer = comido)
Hemos -ir = -ido (vivir = vivido)
There are of course a list of irregulars as well we you can find in De Acuerdo P.67. You can revise the Present Perfect by clicking here.
However we can also use the Past Participles with Ser to construct the Passive Voice. This is normally seen in journalistic articles so it’s important to be able to recognise it even if you don’t use it. Click here for a quick rundown on this, make sure you practice using the quizzes on the left hand side of the page.