i have answered this just as many times as you have asked it
once more and i'll begin to consider it trolling
it is all available in books (i know you read for backstory on other subjects) OR it is all available at a mere google search or just go to wookiepedia
one answer-- starkiller base was built in the Unknown Regions of the galaxy--areas never explored or inhabited by peoples from the galactic empire/republic worlds
http://starwars.wikia.com/wiki/Starkiller_Base
the new republic did not do anything-or very little- to stop the first order mainly because its senate did not believe they were an issue and many did not even accept that they existed. many believed leia and or followers were just a bunch of ex -rebel military who did not want to give up power and were looking for an enemy to have the NR raise funds to build a new military
once the Hosnian system was destroyed and the NR senate and small defense force with it, mos tof the rest of the NR surrendered to the first order to avoid destruction
this is one reason why Leia and her 'all chic command group' were headed for the outer rim and whatever promised force was there to help out the resistance since all NR planets had surrendered
http://starwars.wikia.com/wiki/First_Order
but starkiller base was a dumb idea in the movies and too grandiose. leia and her gal pal's decision to basically sacrifice everyone just so Leia could get to the outer rim and hope that Luke returned, was even a far more idiotic an idea