Hello!
You can use a digitale edge as start trigger (is you have such a digital signal you want to use to synchronize all your generation) or you can use a software start trigger to start the generations.
You can use the ConfigureDigitalEdgeStartTrigger() or the ConfigureSoftwareStartTrigger() functions to configure them.
With SendSoftwarEdgeTrigger() you can then generate the software trigger which starts the generation of your waveform.
The informations about those functions can also be founded in the help (Start->Programs->National Instruments -> NI-HSDIO -> NI Digital Waveform and Analyzer Help)
Best regards
Ken