1)Gemfileにspree関係のgemを追加

# 今回はmysqlを利用する
gem 'mysql2'

# spree
gem 'spree', github: 'spree/spree', branch: '3-0-stable'
gem 'spree_auth_devise', github: 'spree/spree_auth_devise', branch: '3-0-stable'

2)$ bundle install --path vender/bundle
3)rails g devise:install
4)database.ymlにDatabase設定を記載

database.yml

development:
  adapter: mysql2
  database: mystore
  username: root
  password:
  encoding: utf8

test:
  adapter: mysql2
  database: mystore_test
  username: root
  password:
  encoding: utf8

5)config/initializers/devise.rbを修正

config/initializers/devise.rb

  # The secret key used by Devise. Devise uses this key to generate
  # random tokens. Changing this key will render invalid all existing
  # confirmation, reset password and unlock tokens in the database.
  config.secret_key = 'シークレットキーの値が入っています'
.
.
中略
.
.
  # ==> Mailer Configuration
  # Configure the e-mail address which will be shown in Devise::Mailer,
  # note that it will be overwritten if you use your own mailer class
  # with default "from" parameter.
  # メーラー設定
  # Devise::Mailerのメールアドレスを設定します。
  # もし、デフォルトパラメータの設定されためmailer classを利用するなら、
  # 上書きされることに注意して下さい。
  config.mailer_sender = 'no-reply@sample.com'
.
.
中略
.
.
  # ==> Configuration for :confirmable
  # A period that the user is allowed to access the website even without
  # confirming their account. For instance, if set to 2.days, the user will be
  # able to access the website for two days without confirming their account,
  # access will be blocked just in the third day. Default is 0.days, meaning
  # the user cannot access the website without confirming their account.
  # 確認設定
  # ある期間ユーザーはアカウントを確認せずにサイトにアクセスすることが出来ます。
  # ~ 以下略 ~ (許可される期間が2日とか3週間とか何とか...)
  config.allow_unconfirmed_access_for = nil
.
.
中略
.
.
  # Email regex used to validate email formats. It simply asserts that
  # one (and only one) @ exists in the given string. This is mainly
  # to give user feedback and not to assert the e-mail validity.
  # config.email_regexp = /\A[^@]+@[^@]+\z/
  # メールアドレスのバリデーション
  config.email_regexp = /\A[[^@\s]&&[ -~｡-ﾟ^,]&&[^,]]+@([[^@\s]&&[ -~｡-ﾟ]&&[^,]]+\.)+[[^@\s]&&[ -~｡-ﾟ]&&[^,]]+\z/
.
.
中略
.
.
  # Time interval you can reset your password with a reset password key.
  # Don't put a too small interval or your users won't have the time to
  # change their passwords.
  # パスワードをリセットするためのキーでリセット出来る期間について。
  config.reset_password_within = 2.weeks
.
.
中略
.
.
  # ==> Scopes configuration
  # Turn scoped views on. Before rendering "sessions/new", it will first check for
  # "users/sessions/new". It's turned off by default because it's slower if you
  # are using only default views.
  # スコープの設定
  # ログインしてないと接続できるのはサインアップだけとか何とか...
  config.scoped_views = false

6)rails g spree:install
対話形式で設定