Branding your chart with a logo will increase your online presence and ensure that you get attribution for your data, especially when your public charts are shared across web sites. In order to add logos or images, you need to upgrade your account to Platinum.
Once you upgrade, go to your Logos and Images menu and and select Insert Image or Logo.
You can add numerous images or logos to your chart and provide unique hyperlinks to each one (Logos and Images > Manage Images).
Save Images to Templates
Save the images and logos to templates to save yourself from uploading the images each time and to ensure precise placements (Logos and Images > Manage Images > Include in Template, then Chart > Save Design as Template) which can be applied to other charts.