it's here;You hear it mentioned a lot, it's in the lore and in the books but where is it on the galaxy map? I just don't know:S
The frontier is the edge of human occupied space. Go to your galaxy map and set the view to map, allegiance and remove the none option. Scroll around, where the colored dots stop - that's the frontier.
It'll probably take a while before the next wave of colonization really picks up. The FrameShiftDrive is still very new and only small ships use it. The old Witchspace hyperdrives used in the 3250's would take days to weeks to travel to the next star/planet, years to decades to cross known space. Look at the effects when an Farragut or Majestic appear, that's not a FSD flash of light and they don't leave FSD wakes when they leave. Can they even make a FSD for a 150,000 ton hull?