You have go to aa.com or call AA so they have it correctly in their system. QR/amadeus has a way to add a DOCx SSR with you KTN, but most likely it will not be transffered correctly into AA's system.
Also note that sometimes precheck is not 'granted' when connecting to/from a non participating carrier. A few days ago I got precheck on UA arriving with LH but not when returning.