You can sharpen your own knives or have them sharpened by a professional at a cutlery store once or twice a year. If you’re going to sharpen them yourself, we’d suggest learning with a lower quality knife that you don’t care about too much. You can use a manual or electric sharpener which you slide your blade through, but these can shave more steel from your blade than necessary or damage your blade if not used carefully. A whetstone is usually a better bet, ideally a two-sided whetstone with a coarse grit on one side and a fine grit on the other. After you’ve sharpened your knives, we’d also recommend going over them with a honing steel, meant to smooth and straighten the edge of the blade and make it true.