The strings are tuned as follows (in standard tuning) from Low to High : E A D g b e ... Capital & small letters refers that the small ones are of higher pitch.
About the electronic tuner ... You just said it has a needle , so I don't know wether it's an analogue or a digital one ...
But anyway , if it has a mic that catches the note acousticaly , then it can tune an acoustic easily , if it has to be connected by a cable to your guitar , then you'll need an acoustic cable (forgot it's name) to tune an acoustic .
Generaly , acoustic guitars are tuned by a tuning fork.