Add user to bumblebee group with
$ gpasswd -a $USER bumblebee
In /etc/bumblebee/bumblebee.conf
add
[driver-nvidia]
# Module name to load, defaults to Driver if empty or unset
KernelDriver=nvidia
PMMethod=bbswitch
In /etc/bumblebee/xorg.conf.nvidia
set BusID via lspci
(e.g. PCI:01:00:0
).