The easiest way to get your AA number on to the account, assuming your don't have a household account, is to book the reservation not for yourself, but for someone else with the same name, address and date of birth etc. This is just a mechanism to have an empty screen to put on the details. Then go to the seating area after completing the booking, find the AA PNR which is on that screen, then go to the AA app withe that new PNR to complete the booking including Aadvantage number and KTN. Otherwise Twitter is what some people to use to do this.