I really like this pack, it changes Minecraft in a whole new way ^^.
But now 1.9 is out and I'm waiting for an update ... hope it will come soon.
Oh, I got the mistake
You have to start (by double-clicking) the downloaded .jar file and klick "extract", then you navigate to the folder you want to place the file in.
If it is extracted you put the "OptiFine_1.9_HD_U_B1_MOD.jar" (the name is varius, but the "MOD" is the essencial part) into your mods folder.
That should work