this depends on what device you want to control using the MF634 board, and what is the type of signals that the device is using to communicate. For example, for a device using analog signals, you would use the Analog Input and Analog Output blocks, in a way shown by the sldrtex_controller example. If your device understands a different type of signal, you would use the corresponding I/O blocks. Please try to take a look at all the examples shipping with Simulink Desktop Real-Time, try to find the example that is most similar to what you are trying to do, and start from that example.
Good Luck, Jan