You can find the specific instructions for creating a GMail signature on any device here.
Where do GMail signatures show?
Whenever you send an email using GMail (such as clicking a link which opens GMail itself) it will include the signature you created in GMail. This is because you are composing the email from within GMail.
My Kunversion+ emails don't have my GMail signature? Why?
When the system sends emails automatically, it cannot read your GMail signature from your Google account, so we compile a signature based on your profile info.
I am trying to send an email from Kunversion+. My signature is not showing. Why?
When we trigger a pre-written email for you to send from a link you click in the system, it overwrites the signature. It's a technical limitation. The best workaround is to create a canned response with just your GMail signature. That way you can quickly and easily insert it when you need to.