You can add your logo to the menu area on your website.
To do this go into Site Settings > Look and Feel > Menu > in the logo section click the icon, browse your harddrive and choose your logo
There is the option to link the logo. This means when someone clicks on the logo they are taken to a page on your website or an online form etc. (Note - this is optional).
When you view your page the logo appears to the left of the main menu.