You can add your logo to emails and the login screen of your widget by navigating to "Settings > Account Settings" inside your Glow account.
Once in account settings, you'll see an upload field where you can upload your logo.
Select your file and click "Save Settings". You will now see your logo on the settings page. If you'd like to remove your logo, you can click the "Remove Logo" checkbox and click "Save Settings".
Once your logo is uploaded, it will be automatically placed in your email templates (if you haven't already customized the emails) and included on the login screen of the loyalty widget on your site.