You mean in your signature?
Navigate to the signature link (see attached photo) and copy/paste the relevant code there. Probably what you tried to post in post #1.
If it doesn’t work, you likely chose the wrong type from the choices given wherever you are grabbing the banner from. They usually list more than one type, for Bulletin Boards (BBCode), Facebook, and others.
Keep trying others until you find one that works. And double check that you didn’t accidentally miss anything when copying the code.