installing sketches for dht22

I have been trying to install any of the subject sketches from the many that appear on my search. Upon compiling the sketch I consistently receive the attached erroArduino: 1.6.9 (Windows XP), Board: "Arduino/Genuino Uno"

C:\Documents and Settings\Richard\My Documents\Arduino\TEMP-HUM\TEMP-HUM.ino:82:19: fatal error: dht11.h: No such file or directory

#include <dht11.h>

^

compilation terminated.

exit status 1
Error compiling for board Arduino/Genuino Uno.

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What am I doing wrong?

Install the dht library