From a Home screen, navigate: Apps Apps icon > Messages Messages icon.
If prompted to change the default SMS app, tap OK to confirm.
Tap the More icon Menu (located in the upper-right).
Tap Settings.
Tap Signature.
Tap the Signature switch (located in the upper-right) to turn on Switch on or off Switch off.
Note A signature is automatically attached to each sent text message when switch is in the on position.
To edit the signature when the setting is on:
Tap Edit signature.
Enter the signature then tap SAVE (located in the upper-right).