1- Channel creator will also be the Channel Owner, you can add another co-owner by following below steps.
In the left vertical navigation, click on the required Channel directly to load the Channel Page, or click on the “Explore” link in the top header, then tap on the channel name.
2- Click on the “Edit” button in the right.
3- The Edit Channel Page will be opened as below:
4- Add Co-Owner in the "Owner" box. You can type in the user email or select existing user from the drop down to assign a Co-Owner, and then click on the "Save" button when finish.