Cut your string about 1 foot longer than your desired end length in order to leave some extra room on the ends of the string for hanging it up.  

Line up the balls in your desired color pattern

Thread the string through your needle and take the needle and thread it through the center of the first ball.

Slide the ball down to the bottom of the string.  Tie a small knot at the end of the string to keep your ball from moving around.  

Continue creating your pattern until your garland is the desired length.  Finish with another knot at the end to keep your balls from sliding off the string. 

Hang up and enjoy!