To craft netherite, you need to put 4 netherite scrap and 4 gold ingots into the crafting table menu (placement doesn't matter). You get one netherite scrap by smelting a piece of ancient debris in a furnace.
In short, you'll need to get Ancient Debris in the Nether, smelt it, then combine the scraps with Gold to get Netherite Ingots that can be used for crafting. It's an arduous process, so we've...