I also don't know which tutorial that might be.
When you open a multiple page PDF with Inkscape, Inkscape can only open one page (as far as I know). When you try to open any PDF file, you will first see a small dialog with a few different options to choose from. At the very top is a small dropdown menu where you can choose which page you want to open.
Although if you install a special extension, I think you can open multiple page PDFs. There are 3 different extensions, and as far as I could see (when I recently needed one) they all work (and install) a little bit differently. So if you have one of these extensions installed, please tell us which one.