There are a number of ways to create a Postscript file. Enough for at least another article. But let's assume that you have a Postscript file that you want to run through ps2pdf. What do you do?
Open a terminal window and change to the directory containing the Postscript file. Then type ps2pdf followed by the name of your Postscript file. For example:
ps2pdf penguin.ps
This creates the file penguin.pdf.
Note: Running ps2pdf on some Linux distributions like Knoppix, might not work. Try using the command ps2pdfwr instead.