Copy the submitToClarisse.py in a place you like, i.e. your home directory
Open the submitToClarrise.py script and change the lines from 9 to 14 to reflect your Dispatcher settings and installation path of Mrtool
Open Clarisse, and right click on your shelf, then select Add Item
Give a title to the item like Submit to Muster, give a description as well if you like
Choose the item category of create a custom Muster category
Select the submitToClarisse.py file from the Script path selector
Assign a Muster icon to the script, by selecting Custom icon, and picking the icon from your Muster installation path $installpath/templates/icons/muster.png