Click OK then navigate to the game folder, for example it will look something like this.
C:\Program Files (x86)\Steam\steamapps\common\Watch Dogs 2\
then just highlight watchdogs2.exe and click OK.
Did you look up the Windows Event Viewer and get anything about an app crash or something?
Yes and what I can found is that "System was rebooted without clean logo off. Possibility caused by error or power shortage." Where EXACTLY I need to look for more info?