For origin, always use this.mxform. Don’t worry too much about what this is, this will work. I believe it is just letting the nanoflow know that any page activity involved is connected to the form / page the nanoflow runs from.
For context add the input parameter of the nanoflow, which is typically a Mendix object itself. It should be of type ‘Mendix/lib/MxContext’ like all Mendix objects which you interact with via the Client API