Linux – XFCE Menu editor and lxmed

The easiest:
#Application Menu -> Settings -> Main Menu

Otherwise download and install lxmed

# XFCE Menu editor
cd /tmp
wget http://freefr.dl.sourceforge.net/project/lxmed/lxmed-20120515.tar.gz
tar -zxf lxmed-20120515.tar.gz
cd lxmed
sudo sh ./install.sh
#Application Menu -> Settings -> Main Menu Editor
#or via console
lxmed

Uninstall

sudo sh /opt/lxmed/uninstall.sh