This option is available on our Premium membership. You can add it right after welcome screen in My Invoices, the first entry. If you are using My Invoices and have invoices already issued - click "new invoice" button, next click on settings icon, in the upper right corner, and select "invoice personalization". A new screen will be displayed and you will be able to add your logo there. The maximum size of file is 1 mb and the allowed formats are: JPG and PNG.