I assume this is the boat you ordered new in Dec 2020? I would hope the dealer would install the fenders. If not, I hope they gave you the assembly instructions and hardware.
Can you clarify if your asking about trailer fenders or boat bumpers? For boat bumpers if you don’t have cleats on your boat, I’ve used these on my pontoon. Surprised by the price of these if they are 15.00 each. It isn’t clear if they are 15.00 each or 15.00 for 2. They work well.