You can easily add or change a website logo. From Left Toolbar go to
SETTINGS > Logo and Website Title, it's where you can set your website title (it's required even if you want to show logo only, it'll be used in META tags, e-mails and few more locations)There's an option to show website name and logo or to show website logo only, if your logo contains website name already.
It's possible to customize the way your logo shows in website header, there's a shortcut to Menu Designer section below your logo thumbnail, but you can access it from Left Toolbar > DESIGN > Menu Designer > Menu Title/Logo. In menu designer, you can set your logo maximum height, and spacing around it, you can also make your logo appear in its own line instead of in the same line as website menu.
