The General output settings (GOS) application can be used to change/update company logo's. 

If you have access to this application, you can upload the new file, and set it as active.

(Access is found in the role: Output Administrator -> Manage print and email configurations/settings)

The logo will usually show in the top right corner on standard designs.

All logo files must be wither .jpg or .bmp format.

The logo will scale proportional in the given area set of for the logo.