The required images are recommended, the logo and the icon are used when the invoices and tickets are generated, this way they will branded and make your business look even more professional.
To add/edit your Logo/Icon files go to:
Dashboard ➡️ Top Menu with “Your Company Name” ➡️ Provider Info

In the SERVICE PROVIDER EDITOR choose Logo/Icon

The images can be uploaded by clicking on the upload button:

Once they are into place, they will automatically show up in your invoices and tickets as shown below:
