The official vIDE page at PUBInstallation notes:

You can set the VIDE_HOME environment variabile by typing th folowing at the commmand line prompt (or, you can alternatively put these lines into /etc/profile or autoexec.bat):
$export VIDE_HOME=<path_to_your_vIDE_installation> on UNIX,
or:
set VIDE_HOME=<path_to_your_vIDE_installation> on Microsoft- based platforms.