Make sure that you first have Node.js and npm installed. Then install sequelize.js with npm

npm install --save sequelize

You will also need to install supported database Node.js modules. You only need to install the one you are using

For MYSQL and Mariadb

npm install --save mysql

For PostgreSQL

npm install --save pg pg-hstore

For SQLite

 npm install --save sqlite

For MSSQL

npm install --save tedious

Once you have you set up installed you can include and create a new Sequalize instance like so.

ES5 syntax

var Sequelize = require('sequelize');
var sequelize = new Sequelize('database', 'username', 'password');

ES6 stage-0 Babel syntax

import Sequelize from 'sequelize';
const sequelize = new Sequelize('database', 'username', 'password');

You now have an instance of sequelize available. You could if you so feel inclined call it a different name such as

var db = new Sequelize('database', 'username', 'password');

or

var database = new Sequelize('database', 'username', 'password');

that part is your prerogative. Once you have this installed you can use it inside of your application as per the API documentation http://docs.sequelizejs.com/en/v3/api/sequelize/

Your next step after install would be to set up your own model

There are two ways to define models in sequelize; with sequelize.define(...), or sequelize.import(...). Both functions return a sequelize model object.

1. sequelize.define(modelName, attributes, [options])

This is the way to go if you'd like to define all your models in one file, or if you want to have extra control of your model definition.

/* Initialize Sequelize */
const config = {
    username: "database username",
    password: "database password",
    database: "database name",
    host: "database's host URL",
    dialect: "mysql" // Other options are postgres, sqlite, mariadb and mssql.
}
var Sequelize = require("sequelize");
var sequelize = new Sequelize(config);

/* Define Models */
sequelize.define("MyModel", {
    name: Sequelize.STRING,
    comment: Sequelize.TEXT,
    date: {
        type: Sequelize.DATE,
        allowNull: false
    }
});

For the documentation and more examples, check out the doclets documentation, or sequelize.com's documentation.

---

2. sequelize.import(path)

If your model definitions are broken into a file for each, then import is your friend. In the file where you initialize Sequelize, you need to call import like so:

/* Initialize Sequelize */
// Check previous code snippet for initialization

/* Define Models */
sequelize.import("./models/my_model.js"); // The path could be relative or absolute

Then in your model definition files, your code will look something like this:

module.exports = function(sequelize, DataTypes) {
    return sequelize.define("MyModel", {
        name: DataTypes.STRING,
        comment: DataTypes.TEXT,
        date: {
            type: DataTypes.DATE,
            allowNull: false
        }
    });
};

For more information on how to use import, check out sequelize's express example on GitHub.