Tvheadend

Dear team,
I have successfully install the HTS Tvheadend 4.3-1687~g7fdc6f0 in Ubuntu Server 16.04 LTS.
This server has TBS-6522 card.
LNB 0 is the direct input from my ku Band Dish and My satelite is G-sat 15 (India - WB).
I have dvb-s/s2 http streaming successfully. My moto is to deliver IPTV stream to my users via someway so that b.w. can be saved.
Through IpTv android app via adding "http://myip:9981/playlist" - I successfully get all streaming.
Through vlc player upon adding same url for http streaming goes absolutely ok.

But I am absolutely want this stream to give my viewers (FTA channels only) as multicast stream.
I do not want that my viewers use http streaming url . Instead I want them to use rtp@multicast ip:20000 as a url or simply I want multicast out put to my users.
I want to save the bandwidth.
I do not have much budget to purchase any related server.
I need this multicast streaming any how to be work.

Please suggest with detailed guideline , links for "learning how to" as much as necessary.
What I have to do for saving bandwidth for streaming other than http?
Is multicast is the only option or something different method(s) is/are there ....Please enlighten me in all this aspects.

Please give me idea as I am stacked totally.