cannot add the library via NPM. Please somebody get me out of this confusion !!!!

[explorer977]

i have a simple project with just 3 files: index.html styles.css app.js and package.json
and i tell this to convey that this isn't in react or any other dev server.
when i follow the instructions given in the getting started page of swiper library
i can install that via cdn
but having trouble with it when i want to install it via NPM
it simply doesn't appear or work.
i appreciate anyone would help.
and i have a request for him
please do the instructions yourself with your own project and test it via cdn and npm
i',m sure you'll get what i mean