Sorry to hear about your car trouble.
If you have rental reimbursement coverage, you should contact your agent and file a claim. They will most likely take control, providing you with a rental car as soon as they can. Some carriers have preferred rental companies, and you may get a discount if you rent a car through one of them.
However, if you’re not at fault in an accident, the other driver’s insurance policy will likely cover the cost for you to obtain a rental car.