$ npm install <module> --save

$ npm install <module> --save-dev

var gulp = require('gulp');

gulp.task('default', function() {
  // place code for your default task here
});

Execute it:

$ gulp

If there was not a default but, for ex., deploy:

$ gulp deploy

var gulp = require('gulp')

gulp.task('deploy', function () {
    gulp.src('app/*.js')
        .pipe(gulp.dest('dist'));
});

gulp.task('deploy', ['prior-task1', 'prior-task2'], function () { ...