To modify the footer go to 'Preferences' located on the left menu of the Emercury Panel. Click the little arrow to the left of the word Preferences and this will drop down the submenus. Click on 'Email Footer'
Enter all information in all the fields. If you want to upload your own logo then choose the 'browse' button to upload your logo and select the box that says Show Logotype. If you don't want to upload a logo then uncheck the check box that says Show Logotype. Once you are done choose the 'Save Settings' on the top bar. Note: if you want to revert back to the original footer provided by Emercury choose the Reset to Default button on the top bar.