if i try to include dht.h library it gives me error it says no directory found dht.h
Make sure that you have installed the correct library in the correct place, and that you use the correct name. (It's case sensitive. Did you mean <DHT.h>?)
i tried with dhl.h and DHL.h but does not work how i install all library for arduino i am using linux ubuntu 15.10
I imagine that the same place where you got your code will also have a link to the library.
You should have a 'Libraries'-folder somewhere. I don't use Ubuntu for Arduino development, do I can't tell you where it is. I'm sure you can find it. For me it is next to my sketches folder.
In the Libraries folder, you can see that each library has its own subfolder, with a .cpp and .h and possibly some more files.
After you add your own, you have to relaunch the IDE for it to be recognized.
Also, you can look in Menu -> Sketch -> Include Library -> Manage Libraries, and see if it is in there.
i installed library dht.h but gives me the error i can not understand what's going on
i resolved everything is ok thanks