To send an image to the display, you'll first save it on the display memory card, you can do this by putting the unit in mass storage mode and transferring your image (make a note of the file name). Next you'll out the unit back into regular communication mode and load the bitmap into a buffer. Finally, you'll display the contents loaded into that buffer to the screen.
You can find all required commands in the manual
, and might consider using our simple GUI tool
to get a feel for the unit before beginning your C# development.