The answer to 'how to repair drip edge' is to replace any damaged or loose drip edge along the roofline. Drip edge is a metal flashing that helps direct water away from the roof edge and prevent water damage to the home's exterior. To repair it, you'll need to remove the old drip edge, clean the surface, and install new drip edge using roofing nails or screws.
Be sure to match the new drip edge material and size to your existing roof. It's also important to properly seal the edges to prevent leaks. This is a fairly straightforward DIY project, but you may want to call a professional roofer if the damage is extensive or you're uncomfortable working on your roof.