The third party coverage are included in the rental, and you have following options for the rental vehicle:
1) if you have auto insurance and it covers rental vehicles, you can use it and decline the collision and damage waiver;
2) if you are using a gold credit card or some other card which provides coverage for rental vehicles, you can also decline the collision and damage waiver.
3) if you don't have auto insurance or a credit card that covers rental vehicle, you can buy the collision and damage waiver from the rental company which is around $20 per day.
4) you can simply decline the collision and damage waiver, but then you are responsible for any damage to the rental vehicle.