What model is your Samsung Galaxy Note 3?
Type this in google: (The device model number) and CF-Auto Root. If you can't find any CF-Auto Root(s) for your Samsung Galaxy Note 3 variant then try the other rooting alternative below.
You can alternatively use the program called iRoot (which you install on your computer and run). It is a simple 1 click application that automatically roots the phone for you. You will need to enable USB debugging of course.