how can i make my horn honk when i lock my doors

Have a dealership program this setting into the BCM.  It was likely turned off by accident.

No need to take it to the dealer, look in the owners manual. Mine was set not to beep from the factory.

This feature allows you to program your Remote
Keyless Entry (RKE) feedback to a preferred
setting.
To set your choice for this feature, perform the
following steps:
1. With the engine off, turn the key to LOCK.
Do not remove the key from the ignition.

2. Press and hold the lock and unlock buttons
on the RKE transmitter at the same time.
Hold both buttons until the DIC display shows
the current RKE feedback mode.

3. To view the next available mode, press and
hold the reset stem for about two seconds.
Release the reset stem and press and
hold again to view each mode.
4. Once the desired mode is shown on the DIC
display, briefly press the reset stem to set
your choice. The DIC display will then clear.

The following are the available modes:
RFA 1 (default): This mode flashes the parking
lamps when you press the lock or unlock
buttons on the RKE transmitter.

RFA 2: This mode flashes the parking lamps and
sounds the horn when you press the lock button
on the RKE transmitter. This mode also flashes the
parking lamps when you press the unlock button
on the RKE transmitter.

RFA 3: This mode flashes the parking lamps
and sounds the horn when you press the lock or
unlock buttons on the RKE transmitter.

RFA 4: This mode disables RKE feedback. There
will be no feedback when you press the lock or
unlock buttons on the RKE transmitter.