First, it seems that ~/.config/lxsession/LXDE-pi/autostart does not exist by default.
- copy the autostart
cp /etc/xdg/lxsession/LXDE-pi/autostart ~/.config/lxsession/LXDE-pi/
- open the autostart with nano
nano ~/.config/lxsession/LXDE-pi/autostart
cp /etc/xdg/lxsession/LXDE-pi/autostart ~/.config/lxsession/LXDE-pi/
nano ~/.config/lxsession/LXDE-pi/autostart