To feature a channel in your marketplace of on the homepage, first you need to connect to the channel. You need to connect to the channel even if it is a channel you have created our self.
From your Ecosystem Admin dashboard, in the Manage Marketplace section, click Discover
On the following page you can enter a search term to find the channel you want to connect to.
Click to connect with the channel.
Next, head to the marketplace setup, from the Marketplace > Setup section of your Ecosystem Dashboard.
In the channels section, search for the connected channel
Select from the list, and click "Add" to feature it.
The channel will now be featured.