MGM Grand is a venue in or near Las Vegas that is most often used for Basketball
There is plenty of parking everywhere as long as you are staying at the hotel, gambling, or seeing an event so you can park at the actual MGM Grand but just make sure to get there early on a fight night. There is also free valet but again make sure to get there early.
Parking is provided by MGM and is free. It's recommended that you arrive an hour early. Even valet parking is free (tipping recommended).