The images must be in a format called ppm (portable pixel format). Many image editors support this format, including the free open source application Gimp.
The image needs to be 16 pixels high, but can be wider than the 32 pixels of the display, as the text will scroll horizontally.
This image was created in GIMP. Notice that the background needs to be black.
Use the File->Export command on GIMP to export the image as ppm and then transfer the file into the directory /home/pi/display16x32/rpi-rgb-led-matrix on your Raspberry Pi. You can just use a flash drive to copy the file over.
Run the command again, this time using the name that you gave the file:
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