While you can certainly add a logo directly to your survey, creating a style template with your logo will allow you to re-use the same style template for multiple surveys so you don’t have to duplicate your work. Styles templates are reusable templates that you create under the main Styles menu and then apply to your survey(s). Style templates allow you to:
Click the Edit Header Content option and then use the image button options upload and resize your header image. You may also add text to your header or other HTML using the HTML source code (<>) button.