Hi Susan- The great thing about Avere when used as the auxiliary/helping verb in past tense (Ho,Ha,Hai, Abbiamo, etc) is that you don't have to worry about modifying the verb for gender/number- it always ends in 'O'. There is an exception to this (of course!) when you use a Direct Object Pronoun in the sentence, which you'll get to later.
Examples:
L'ho portat o (I brought him)
L'ho portat a (I brought her)
Le ho portat e (I brought them - feminine)
Li ho portati (i brought them - masc/mixed)

Hope that helps!