It is a common misconception that you should tap your razor against the sink or a hard surface to remove trapped hairs. Although it may well dislodge the hairs, the impact can also damage the cartridge. Instead, simply rinse your blades in water, letting it run from the back to the front of the cartridge, shaking it firmly to remove debris. When you've finished shaving, store your razor in the open air to let it dry, ideally in a vertical position.
To remove and replace your Fusion5 cartridge, simply press the easy-release button at the back. Take a replacement cartridge head and slide the handle into it until you hear the click indicating that it's in place.