To obtain the channel id you can view the source code of the channel page and find either data-channel-external-id="UCjXfkj5iapKHJrhYfAF9ZGg" or "externalId":"UCjXfkj5iapKHJrhYfAF9ZGg".
UCjXfkj5iapKHJrhYfAF9ZGg will be the channel ID you are looking for.