If your site has the logo token in the HTML template you will be able to change out the logo.  You might need to adjust your logo size or the logo dimensions in the CSS in order for it to fit how you like.

1. Log in to your site.
   
   
   
   
2. Click Settings on the admin toolbar.
   
   
   
   
3. Click on the Advanced tab.
   
   
4. Click on the Upload your logo link next to the Website Logo heading.
   
   
5. Click the Choose File button to browse your hard drive for your logo.
6. Once you have selected your logo click the Upload button.