I have installed ELEKTRIK PIANO 1.5, but I can not see the KoreSounds in KORE's Browser.
You need to download the KoreSounds for ELEKTRIK PIANO 1.5. You can find these by running the NATIVE INSTRUMENTS SERVICE CENTER, then go to the Update Manager, then in the small drop-down that says filter you need to select Addon.
If you download and install these then you will see the sounds in KORE. You may need to rebuild the Sound Database in KORE (in File>Options) if they do not show up at first.