As it is not possible to retrieve the logo files directly from the computer, they must first uploaded.
Images may differ.
Enter the Saas user and password again.
Click on upload a new file:
Pick up the image.
Click on next.
It is ready to be loaded:
Go normally to the format editor, click on the image insertion icon.
Select the desired file and proceed normally. (The basic article can be found here)
When it is done, do not forget to delete the file in the loading screen if it is not needed elsewhere.