Answer:
Je suis arrivé(e)
Tu es arrivé(e)
Il/elle/on est arrivé(e)
Nous sommes arrivé(e)s
Vous êtes arrivé(e)s
Ils/elles sont arrivé(e)s
Explanation:
This is the conjugation for "arriver" in passé composé with the verb "être". As a rule of thumb, you've got to memorize the subjects (je, tu, il/elle/on, nous, vous, ils/elles) and the different forms of the verb "être" (to be). From there on in, the conjugation of "arriver" is nearly the same for each different subject. The first three lines of the conjugations (for je, tu, il/elle/on) are all singular, while the other three (nous, vous, ils/elles) are plural. The singular ones don't need an "-s" at the end, while the plural ones do, because they're talking about more than one person. When you see the (e) in conjugation for any verb, it means that you add an "e" to the verb when conjugated for a feminine subject (if you're talking about a girl, you'd write "elle est arrivée" - notice the extra "e" - but if you're talking about a boy, you'd say "il est arrivé" - with no extra "e").
"Arriver" is considered an "-er" verb because it ends in "er". This verb is a part of the first group (1er groupe) because it has the ending it does when in its "infinitif" form - when it's not conjugated. You always conjugate this verb with "être" when conjugating to "temps composés".
Hope this helped! If you ever want further clarification don't hesitate to ask!
