Hi Terri Upon checking the user manual there seems to be no option in the stock messaging app settings. As an alternative, you can try GO SMS Pro. I prefer it over the stock messaging app. I just checked the settings now and there is an option to add signature.

To set signature on GO SMS Pro:
- Open GO SMS Pro
- Tap on Menu and tap on Settings.
- Tap on Send & Receive Settings.
- Put a check on Personal Signature.
- Tap on Signature Content to compose your signature.
- Tap on Ok to save.