Sales channels are a different word for "customer portal" or "branding" inside of hostware. They handle all configuration and allow separation between multiple brands.
Create new sales channel
On the bottom left in the sidebar, create your first sales channel if not done automatically during creation.
Manage sales channel
To edit a sales channel, click on the name on the bottom left in the sidebar. You can then defined the display name, which is often displayed in emails, the navigation and overall branding.
The domain needs to be defined where the customer portal should be accessible. Learn how to change the domain here.