Open the image you wish to make into a half-tone transparency in a graphics editing program, such as Photoshop or Gimp. Make the image black and white if it is not already by selecting "Image>Mode>Grayscale" in the menu options. Complete any final touches such as cropping or editing the image.
Open the image bitmap by selecting "Image>Mode>Bitmap" in the menu options. This will open up the image bitmap dialog box.
Click on the "Method" drop down menu in the image bitmap dialog box and scroll down to select "Halftone Screen".
Set the number of halftone dots and their size by entering a value in the "Output" box. The number you set in this box refers to the number of pixels per inch in the image, so a larger number will result in a more detailed image with more halftone dots that are smaller, and a lower number will result in a less detailed image with fewer, larger halftone dots.
Save your image when you are satisfied with the look of your halftones. Load your transparencies into your printer according to the directions on the package. Open up the "Print" dialog box in your graphics editing program, and select "Page Set Up". Find the drop down menu for paper type, and select "Transparency", then select "Print".