To Watch Free to Air channels on TATA SKY SET TOP BOX
It's just for expeiment Sake, so do at your own risk.
Step wise method
1. Slect right LNB frequency. for it press "Guide button" and navigate to organiser and press 5. then reach to System setting, now press 0, 1, select and for Installer Setup

2) with slect button reach to LNB Setup screen

3) come to User specified Frequency and set value as show .Press back button until you reach Installer Setup screen again.

4) By Installer Setup menu you havr to select Manual Tuning option and select IN4A-18 as your signal source. Press Save Setting option. here you get Signal Strength screen.

5) See now question is from where u wanna get FTA CHs, there are some options like 95.5 E, 75E, 88E, 25.5E 45E, 72E Ect for it you have to get signal first without use of Tataskt Stb i.e from any other FTA STB. after getting signal of a particular bird, connect that Dish antenna LNB with Tatasky STB.

6) Adding channels: Now with dish pointing in the right direction its time to add channels. For that
you need to navigate back to Systems setting screen by pressing back back, back, back and 5 on your remote( press back 3 times and select add channels option) to add channels of your interest which are available on that satellite.

Now select find channels option and you can see the below screen

Wait till channels list displayed
press the yellow button to store or remove the channels. Press the Green or Red button to navigate Up/Down

Press back and Repeat the steps for all the frequencies in the above table.
7) Navigate to the Other channnels option under Organiser menu and press 7 ( or select other channels by scrolling down). To see list of stored channels.

Try and tell the your result.