You can attach your E-signature in the Settings. Click here. This would add your e-signature if you use the system (default) footer.
For Pro subscribers with a custom footer design, we can help you.
You can attach a clear, high resolution picture of your signature (on white background) in the support area.
We'll help import it to your account. 👍🏼
Note: The prescription custom header and footer editor is part of the Pro plan - you have access to it within the first 30 days upon signing up.