This is a stupid question but..

[mattwestwick]

............................................________
....................................,.-'"...................``~.,
.............................,.-"..................................."-.,
.........................,/...............................................":,
.....................,?......................................................\,
.................../...........................................................,}
................./......................................................,:`^`..}
.............../...................................................,:"........./
..............?.....__.........................................:`.........../
............./__.(....."~-,_..............................,:`........../
.........../(_...."~,_........"~,_....................,:`........_/
..........{.._$;_......"=,_......."-,_.......,.-~-,},.~";/....}
...........((.....*~_......."=-._......";,,./`..../"............../
...,,,___.\`~,......"~.,....................`.....}............../
............(....`=-,,.......`........................(......;_,,-"
............/.`~,......`-...............................\....../\
.............\`~.*-,.....................................|,./.....\,__
,,_..........}.>-._\...................................|..............`=~-,
.....`=~-,_\_......`\,.................................\
...................`=~-,,.\,...............................\
................................`:,,...........................`\..............__
.....................................`=-,...................,%`>--==``
........................................_\..........._,-%.......`\
...................................,<`.._|_,-&``................`

If you have the steam version it will have already been downloaded and you can run it from the Amnesia launch menu by clicking the "Justine" button. If you dont have steam version then just wait. That is all.