Why my dlc nit letting me hve tha cars

I think you may need to elaborate a little on that. If you own the Speedcross DLC, the cars are unlocked and available to buy in the dealership(s) (if I recall correctly). If you're on PS4 and have the Deluxe Edition, there's a problem with the DLC which they're working on. What exactly is the problem you're experiencing?

You have to beat all of the Speedcross events to unlock the Infinity and the Mini. They will be free at all dealerships. You unlock the Speedcross dealership after beating the Speedcross events also.

For me, at least on PC, the cars are already unlocked at all dealerships, and the Speedcross dealership was open right away, before I'd even started any of the new events :0)