No, you don't buy the credit card insurance. It comes with having the card. Some credit card companies charge a yearly fee for their card some don't, but in general they offer the insurance as a perk.
I have Diners Club and pay a yearly fee. It is higher than MasterCard and Visa, but it has features I use. One of them is their auto rental insurance. It is also a primary insurance, meaning if I get into an accident they take care of the claim settlement. My personal auto insurance doesn't become involved.
Check with your credit card company to see if this is one of their perks.