Here is a step-by-step guide for what I did to make Nvidia Optimus work on Kubuntu 15.10 64-bit. Note that I describe the user friendly way because it's meant for all users to be able to do it.
- In the Device Manager choose the recommended driver, in my case nvidia-352
- If you don't have it already, in Muon Discover find Muon Package Manager and install it
- Start Muon Package Manager, type nvidia
- Make sure all of the following packages are installed, as you will probably have to install some of them

- From the menu start Konsole and type
sudo kate /etc/bumblebee/bumblebee.conf
- Change the following lines
Driver=
to
Driver=nvidia
and
KernelDriver=nvidia-current
to
KernelDriver=nvidia-352
and
LibraryPath= Sorry I don't remember what was there
to
LibraryPath=/usr/lib/nvidia-352:/usr/lib32/nvidia-352
and
XorgModulePath= Sorry I don't remember what was there
to
XorgModulePath=/usr/lib/nvidia-352/xorg,/usr/lib/xorg/modules
- Reboot
- From menu start Konsole and type
optirun steam if you play games via Steam
- Enjoy!