NinjaPoints is an addon created on request by another rogue.
/npoints (or /np) will bring up the options menu.
Optionally, you can go through Blizzard's Interface options menu.
If you like NinjaPoints add it to your favorites and tell your friends about it.
Adding your own sounds:
Take your sound file and place it in the NinjaPoints\Sounds folder. Then open up the Sounds.lua file and add your sound with the file path
MySound = "Interface\\AddOns\\NinjaPoints\\Sounds\\mysound.wav",