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.