Receive or learn something, as in I have it on the best authority that he's running again. [Late 1600s]
Possess a solution, understand, as in Is this the new phone number? Do I have it straight? or I think I have it now. [Mid-1800s]
Take it, as in There's some ice cream left; go ahead and have it. This usage is always put as an imperative. [Second half of 1300s]
Have the victory, win, as in We've counted the votes and the nays have it. The related expressions have it over someone or have it all over someone mean “to be superior to someone.” For example, Jane has it all over Mary when it comes to reading aloud. [Early 1900s]
let someone have it. Give a beating, scolding, or punishment. For example, When she gets home Dad will let her have it. [Mid-1800s]
have it off. Have sexual intercourse, as in The two dogs were having it off in the backyard. [Colloquial; early 1900s] Also see the subsequent idioms beginning with have it; not have it.