This capability doesn't exist in the currently shipping LiveCycle ES, but it is in the upcoming release (ES Update 1, aka version 8.2.1).
In ES Update 1, in order to do what you are asking you would need a TaskManagerEndpoint defined for your MyProcess service, so let's presume that you created one and called it MyEndpoint.
The url to immediately invoke this (after a login prompt) would be:
http://servername/workspace?startEndpoint=MyProcess.MyEndpoint