Find them in dungeon, mineshaft, ancient city, woodland mansion, and bastion remnant chests
Fish for them as treasure
Trade with a master-level librarian villager
Use an anvil to rename a nametag after obtaining it
In Creative mode, take them from the inventory
In Bedrock Edition, get them from fishing, chests, or villager trades
In Java Edition, get them from fishing, chests, or librarian trades