Download and install your poster printing program, or install it from discs.
Load your poster printing software, and open the photograph you wish to print. In most programs, you do this by selecting the File menu and then "Open." Some programs have a button or speed key to make this faster.
Set the size of your mural. In most programs this is done through the Print Options or Print Preferences menu option, but your program might have a special menu or menu option for this purpose.
Check the print settings in the program and make them coincide with your printer's defaults, which usually specify 1/2-inch borders. You can also add crop marks -- typically by ticking that check box in the print settings -- to make the pieces easier to cut accurately. Or specify how much the individual printed pages should overlap at the edges for assembling.
Select "Print Preview" to see a version of your final image. The print preview tells you how many pages are required, so load your printer with an appropriate quantity of photo-quality paper.
Print the first page as a test to ensure that your settings are correct. If they are, print the remainder of the image. Trim the edges of each page carefully with scissors or a paper cutter, once they are dry.
Mount the mural one piece at a time on a wall or a custom-prepared surface of appropriate size. An ordinary glue stick or decoupage glue works well enough for a short-term installation.