Tvheadend doesn't have "addons", at least not that I'm aware of.
Also you are talking about a service you have to pay for. Since you are paying them, they should have some incentive to write the software you need in order to use their service. Have you looked on their site?
Many of us use a free alternative called zap2xml - see http://zap2xml.awardspace.info/ . This blog post may be of help if you want to go that route: https://freetoairamerica.wordpress.com/2014/12/03/some-hints-for-getting-free-to-air-satellite-channels-into-the-electronic-program-guide-in-kodi-or-xbmc-or-another-frontend/ . The title is a bit misleading since it has far more to do with Tvheadend than Kodi.
But if you really want to pay for listings for some reason, I think this program might work for you, to create the .xml file that Tvheadend will use: http://mc2xml.hosterbox.net/ It no longer works for its original purpose (Microsoft listings) but may still work with your service.
Either way, the blog post I mentioned above will give you info on how to get Tvheadend to utilize the .xml file created by one of these programs. There may be other ways to do it, I'm just telling you about the ways I am aware of, since no one else has chimed in so far.
