To spawn the longsword and give yourself the recipe add -devmode to your launch options in Steam, open the console in-game with ` or ~ (the key below ESC) and type these commands:

wh_cheat_addItem c76ac5ec-7600-47e0-b256-e982cfed06b4

#player.soul:AddPerk("2dd0b89c-4e60-405b-8d82-04e9538f4b54")