There are two ways this is used:
1.) First is plural/singular.
Has is used with a singular noun. "The dog has the ball"
Have is used with a plural noun. "The dogs have the ball"
2.) Second is used with a particular pronoun.
Present tense
I have
you (singular) have
he/she/it has
we have
you (plural) have
they have
had is used for all pronoun when in the past tense
//: "has" and "have" are called present participle, which means it happened at an unspecified time before now.