To insert a custom logo in the back office:

1. Click Settings > Account > Custom domains from the main menu
2. Click New from the context menu 
3. Enter the host in the Custom domains section
4. Enter the logo in the Look and feel customization  section
5. Click Save

The maximum file dimensions are 130 x 30 pixels. Alternatively, by modifying the CSS through the #DivAzienda selector (removing the padding), dimensions of 200 x 45 may also work.

To modify the file dimensions, it is best to use paint.net