dear hiren
The funda is that your instrument senses the two lobes and assumes that you are flying the set course in ILS.
so in this case you put the course to the final & arm the back course.
the confusion is over the term "back course' which actually means something else (behind the localiser). however the use of this reverses the lobes & you get correct guidance on the outbound. Backcourse can be simply read as reversing the sense. you can also use it in flying the actual back course ( not in India).
.
read this slowly to digest. you can also check with do-228 pilots for clarification.
here you are flying outbound of front course.