Your corporate logo can be easily used in a variety of ways.
Upload your logo file in Settings - Logo. This file must be a minimum of 400px on its shortest side. 400 x 500 will work. 500 x 400 will work. 500 x 399 will give you an error.
Most commonly the Logo will display in the upper left or center of your webpage. Exceptions are possible depending on which theme you have chosen to use.
There is an option for a Favicon file. This is frequently the same as your Logo, but doesn't have to be. It is most commonly used as an icon on a Browser Tab.
This file must have a minimum dimension of 32px on its shortest side.
Note: if you do not replace this Favicon, the SimpleUpdates Favicon will display by default.
An icon for your website may be added to mobile devices using the Web Clip icon.
Not all mobile devices use this option, but for those that do, a bookmark to your site can be added to the device's home page and your Logo will display as the icon.
This file must be at least 180px on the shortest side of the file.
The best look for your logo is for the file to have a transparent background. This allows it to blend well with the background of the website.
Suggest asking your graphic designer for a PNG file with transparent background.
A .jpg file will upload and display, but it will display with a white background. Not an optimal look.