There are instructions in Ubuntu Wiki (see topic "Trackpad").
Basically, you can map right click to two finger click by modifying system preferences and /usr/lib/X11/xorg.conf.d/10-synaptics.conf
:
Section "InputClass"
Identifier "touchpad catchall"
MatchIsTouchpad "on"
MatchDevicePath "/dev/input/event*"
Driver "synaptics"
Option "FingerLow" "10"
Option "FingerHigh" "20"
EndSection
To achieve familiar behavior with the Apple trackpad go to System -> Preferences -> Mouse and select the Touchpad tab. Select Disable touchpad while typing. Deselect Enable mouse clicks with touchpad. Select Two-finger scrolling.
(quote from wiki)