Rangeslider.js does not install - node.js

Question

I am trying to install and use the rangeslider.js API, I have downloaded the latest version and I have gone about installing it via the terminal using both npm and bower install commands. When I try the npm install, i get the following error:
npm WARN checkPermissions Missing write access to /Users/Brian/node_modules
npm WARN enoent ENOENT: no such file or directory, open '/Users/Brian/package.json'
npm WARN Brian No description
npm WARN Brian No repository field.
npm WARN Brian No README data
npm WARN Brian No license field.
npm ERR! path /Users/Brian/node_modules
npm ERR! code EACCES
npm ERR! errno -13
npm ERR! syscall access
npm ERR! Error: EACCES: permission denied, access '/Users/Brian/node_modules'
npm ERR! { Error: EACCES: permission denied, access '/Users/Brian/node_modules'
npm ERR! errno: -13,
npm ERR! code: 'EACCES',
npm ERR! syscall: 'access',
npm ERR! path: '/Users/Brian/node_modules' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.
npm ERR! A complete log of this run can be found in:
npm ERR! /Users/Brian/.npm/_logs/2017-06-30T20_40_33_877Z-debug.log
And when I try the bower install, I get this one:
bower cached https://github.com/andreruffert/rangeslider.js.git#2.3.0
bower validate 2.3.0 against https://github.com/andreruffert/rangeslider.js.git#*
bower no-json No bower.json file to save to, use bower init to create one
The last message on the bower install seems pretty clear, I need to create some sort of jSON file, but I have no idea what the requirements for it are and where I need to save it to. Can anyone help? Before you all suggest it: sudo install does not solve anything.