You can ask them to repair your car themselves or pay to have it repaired. If the dealer will not make all repairs free, think about compromising. A compromise solution will be faster, and maybe better, than the other choices.
Any agreement you reach with the dealer should:
be in writing
say who will do the repairs
say what the repairs will be
say what your cost will be, if any
Be careful about bringing the car in if you owe the dealer money on a down payment or on your monthly payments. Your dealer might refuse to return your car unless you make these payments and treat the return as a "voluntary repossession."
You can ask the dealer (and your lender if you applied for your loan at the car dealer's business) to cancel the contract, take back the car, and refund your money. But dealers (and lenders) usually do not agree to cancel a sale.