- Buy a replacement
– See how the old one was attached
– Remove the old one
– Attach the new one

They sell them at Home Depot. They’re attached with roofing nails or screws. All you need is a claw hammer and/or a power screwdriver.

Kind of what PupnTaco said, but slightly different order…

- See how the old one was attached
– Remove the old one
– Take old one to Home Depot
– Compare old one to Home Depot inventory
– Buy a replacement
– Attach the new one

^ even better.