To transfer ownership of a user's channels to another user, you must be an administrator with subscription rights.
First, select Options on the left and then go to the Manage Users tab.
Locate the user you want to transfer channels from and click the pencil icon to the right to edit the user.
Click on the Transfer Channels button.
Now, type in the email of the user you wish to transfer the channels over to and click Transfer.
A notification will show up on the display to confirm that the channels have been successfully transferred over.