First, you need to be able to scan the slides to create digital image files that you can save/edit on your PC. That requires some hardware -- specifically a scanner, ideally one that can scan slides.

After that, it really depends on what software you have. Some scanners come with their own software, and there are usually pretty good instructions with the manual. Even if you are using Photoshop to deal with the images, you need to use the scanner's software to install the driver or something. But if you use Photoshop, you can usually access the scanner information through the Import feature.