In French, the passé composé is used to indicate action that took place in the past. Unlike the imparfait, these actions neither took place over a period of time, nor are they still occuring. It's basically very similar to the English past tense.
If you need to form a verb in the passé composé, there are at least two very important things to remember. The first is the present tense conjugations of avoir:
Je: ai
Tu: as
Il/Elle: a
Nous: avons
Vous: avez
Ils/Elles: ont
When I first wrote this, I completely forgot about the use of être. It is used with several verbs in the passé composé; generally those that have to do with motion, like aller. I don't have any trick for you beyond that.
Je: suis
Tu: es
Il/Elle: est
Nous: sommes
Vous: êtes
Ils/Elles: sont
The usage is generally the same as with avoir, but there is an excellent writeup here that covers the usage differences between these two.
Second is the special passé composé verb endings.
For verbs with an infinitive form ending in -er: Simply replace the -er ending with the -é ending. Note that parlé is pronounced the same as parler.
For verbs with an infinitive form ending in -re: Replace the -re with the -u ending.
For verbs with an infinitive form ending in -ir: Just drop the r in -ir.
To form the passé composé, simply use the appropriate form of avoir (or être), and then your verb with the appropriate ending:
Present Tense: Je parle à vos soeurs.
Passé Composé: J'ai parlé à vos soeurs.
There are several verbs with irregular forms that are used in the passé composé:
avoir to have eu
être to be été
faire to do fait
dire to say dit
écrire to write écrit
lire to read lu
boire to drink bu
connaître to know connu
croire to believe cru
mettre to put mis
prendre to take pris
suivre to follow suivi
devoir to have to dû
pouvoir to be able to pu
recevoir to receive reçu
savoir to know su
tenir to hold tenu
voir to see vu
vouloir to want voulu
The above list is by no means exhaustive, but if you end up saying something like "Tu elle as voi," a good French speaker could probably figure out what you meant.
Again, note the difference between the passé composé, the imparfait, and the passé simple:
Passé composé is the colloquial past. It describes a discrete event in the past. For example; J'ai parlé could mean "I spoke," "I have spoken," or "I did speak."
The imparfait describes a past event that is ongoing, incomplete, or often repeated (though not a definite number of times). It is often applied to wishes, suggestions, and conditional statements.
The passé simple is the literary past tense. It is usually only used in writing.
The Passé Composé is one of the easiest French tenses to use. Use the irregular verb forms above just like regular verbs; Place the correct form of avoir or être, and then the appropriate verb. This pretty much exhausts my knowledge of it, so if I missed something, let me know.
So, it turns out my French is a little rustier than I thought. There are some additional gender agreement issues that need to be dealt with here. I need to get a book out again and it'll be resolved shortly. What is already here though, should be correct.
Until I get it fixed completely, Linca and eliserh say: Your irregular examples are examples of Participes Passés. The participe will take the gender and number of the subject of the verb if the auxiliary is être. If the auxiliary is avoir, the rule is more complicated : the participe takes the number and gender of the object of the verb, but only if the object is before the verb. e.g., "J' ai vu les amies", but "les amies que j'ai vues."
Again, these gender and number agreements are something that a skilled speaker would be able to figure out if you do them wrong. They're important to know, but you'll probably be understood if you mess them up.