instruction and ruby version

Gemfile

 source 'https://rubygems.org'
 
-ruby '>= 2.3.0', '< 2.7.0' if Bundler::VERSION >= '1.12.0'
+ruby '>= 2.3.0', '<= 2.7.4' if Bundler::VERSION >= '1.12.0'
 gem "bundler", ">= 1.5.0"
 
 gem 'rails', '5.2.4.2'

README.rdoc

@@ -3,3 +3,21 @@
 Redmine is a flexible project management web application written using Ruby on Rails framework.
 
 More details can be found in the doc directory or on the official website http://www.redmine.org
+
+# INSTALLATION
+
+1 Copy `configuration.yml example` and `database.yml example` and paste renaming without the word "example"
+
+2 Install gems: `bundle install`
+
+3 Create database:
+  - create user using `database.yml` infos
+  - grant all privileges to this user
+
+4 Make migrations: `rails db:migrate`
+
+5 run server: `localhost:3000`
+
+# Configure the admin account
+
+Go to the server, click to "connection" link, click to "Forgot your password" link. Follow the link generated in the terminal to reset the password
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