So, here's a Custom Script I wrote that installs the Oracle VirtualBox Extensions:
[MACHINES_MAC]
REMEXEC0=ldkahuna http://coreserver.domain.com/ldlogon/softwaredist/Oracle_VM_VirtualBox_Extension_Pack-4.3.4-91027.vbox-extpack
REMEXEC1=/usr/bin/VBoxManage extpack install /Library/Application\ Support/LANDesk/sdcache/Oracle_VM_VirtualBox_Extension_Pack-4.3.4-91027.vbox-extpack
First, "ldkahuna" grabs the .vbox-extpack file from the core server (or wherever your packages are hosted - it can be any HTTP server). These are by default placed in /Library/Application\ Support/LANDesk/sdcache.
The next line tells the VBoxManage binary to install this package from the path given. It runs this as root.
So, in your case, use the first line to grab the installer file. If it's a .app bundle, then you should zip it up first. I believe ldkahuna automatically unzips the file, but I forget. If not, you can script that in a line immediately afterwards. Your final line should be the command they gave you to type in Terminal.
Let me know if that helps.