Greetings! How to reset 05 CTS Cadillac anti-theft system without taking to dlr. on 2005 Cadillac CTS

Changed battery/alternator on CTS Cadillac. Tried to start vehicle, but not start. Anti-Theft light stay on. Tried 10 mins x 3 = 30 minutes but not luck. Please help!!

Asked by for the 2005 Cadillac CTS
find a good mech with a scanner that can reset for you at min. charge maybe 50.00