when to use have &had

Have is main verb (plural) in the present simple. I have two cars. Have is also used in the present perfect (perfect and perfect continuous) as a helping verb. They have visited many unique places. I haven't been reading for a while. Had is main verb (plural and singular) in the past simple. I had two cars last year. Had is helping verb in the past perfect (perfect and perfect continuous) I had been reading about it for a while at that time.

when to use have & had

has had" is used for the third person singular ( he/she/it). The past perfect form of haveis had had (had + past participle form of have). The past perfect tense is used when we are talking about the past and want to refer back to an earlier past time. She felt marvelous after she had had a good night's sleep