It is enough if the Tvheadend administrator sends you an entry for just one TV channel from a file obtained by entering it in the web browser.
http://Adress-IP-Tvheadend:9981/playlist
e.g. .....m3u list
#EXTM3U
#EXTINF:-1 tvg-id="e6a3525ff10a8b4fc0b6b8e35d4gd5d57f" tvg-chno="1",TV
http://192.168.1.0:9981/stream/channelid/16594438?profile=pass
except that you must add your login and password in this entry, i.e.:
http://login:password@192.168.1.0:9981/stream/channelid/16594438?profile=pass