After you download and install the Multi-Instrument software, the sample code (MyDAQ.dll) can be found in \DAQDAOAPIs\MyDAQVC.zip. It is written in Visual C++. In Multi-Instrument software, the sample code can be demonstrated by going to [Setting]>[ADC Device] and select either "My DAQ Device Type 1" or "My DAQ Device Type 2" in the Device Model selection box. Now, if you start the oscilloscope, you can see the demonstration.
To hook your own hardware with Multi-Instrument, you need to adapt this MyDAQ.dll project to your own hardware and recompile a new MyDAQ.dll, then use it to overwrite the same file under the software's root directory. Launch the software, go to [Setting]>[ADC Device Database] and add a new device for MyDAQ.dll, with parameters corresponding to your hardware.