You have to add it from the Harmony side first, using their instructions to connect to SmartThings. ( Harmony and SmartThings (myharmony.com)) Their process adds the smartapp in your account (this is the only way I know to get it… and when that goes away we’re all hosed) THEN you go into the newly added smartapp and finish the configuration as you were trying to do - BUT it should have the initial auth completed.