You could put something like this into a file (the name of the file doesn't matter, and doesn't need any special file extension, unlike Windows):
You could call it something like updateOM.sh (sh is a common, but optional, file extension for shell scripts).
Make the file executable by executing "chmod +x updateOM.sh"
To test it, just type "./updateOM.sh". The "./" at the beginning is needed.
To create a desktop icon for it, just right-click the desktop and select "Create Launcher", and fill out the details.
Edit: you could also create the script on the desktop (instead of your home folder), make it executable, and skip the "Create Launcher" step.