‘Have’ is used with the pronouns I, we, they, you, and with plural nouns:
‘I have a great house by the river.’
‘We have class at 1pm.’
‘Students have a responsibility to pay attention in class.’
‘Have you been to Melbourne?’
‘Has’ is used with the third person singular, with the pronouns she, he and it:
‘She has a really expensive car.’
‘He has a new pair of shoes.’
‘What a beautiful house. It has huge windows.’
‘Has she seen the new house yet?’
‘Had’ is the past tense of has and have:
‘I had a great house by the river.’
‘She had a really expensive car.’
‘He had a new pair of shoes.’
Photo Flickr:CC Steve Corey