This is the default logo:
You can replace it with your own company logo in My Company > Client/Affiliate Portal
The default logo is 50px x 50px. If you wish to upload a new logo to replace the default logo, it must be a jpeg, jpg, png or gif, no larger than 300px wide by 50px tall and size should be less then 2 MB.
The logo background should be transparent or match the header color. You would use a program like photoshop for this.
Here's a Quick Video: