If you mean something like where the player touches the screen and the bullet go's toward where they touched
you could doing something like set bullet angle toward Touch.Y & Touch.X
For something like where the bullet follows a path premade by your swipe that is something you'll have to work on.
But If I took a shot at it I guess one way would be to spawn Nav points as they player touches then just keeping setting angle of bullet to the next Nav point with some kind of ID attached to it. Sorry can't be of more help.