There are various methods to creating and printing out barcodes, including some software and hardware that will print them directory onto plastic cards. This article walks you through how to install a barcode font on your computer so that you can generate your own through MS Excel or MS Word.
Download Barcode Font
You can install a font on your computer, like any other font, that will render characters as a barcode that a reader will understand. We recommend this TrueType Font, which will generate Code39 1D type barcodes, which any basic reader should be able to pick up.
Fontspring does a good job describing how to install fonts on Mac and Windows.