In Gmail on the web, open Settings → See all settings → General → Signature.
Step by Step
- Open Gmail on the web.
- Select Settings, then See all settings.
- Under General, find Signature.
- Create a new signature.
- Enter and format the information you want.
- Choose signature defaults for new messages and replies/forwards if desired.
- Save changes if Gmail requires it.
If That Doesn't Work
- Mobile-app signatures can be separate from the signature configured on the web.
- Keep business signatures simple so they display reliably across mail clients.