I just received a set of used Bilsteins. How do I tell which strut is for which side? Does it even matter?

Also does the orientation of how I bolt up the 3 top bolts of the strut tower matter? The top seems to spin freely so i'm guessing no?

 

Left and right sides don't matter. Only front and back (duh!)
Correct. Orientation of the top 3 bolts also do not matter as long as they slide through and fit.