Ready made package.json & gulpfile.js (gulp)

http://ift.tt/1QSlgBE

When I download this template, I have ready made package.json & gulpfile.js. How can I install all devDependencies? Should I use defaul construction for every plugin:

npm i [plugin_name] [another_plugin_name] --save-dev

or another quick command?

Shoud I begin work with

gulp init

?