fix Improve README.md #3

README.md

@@ -1,5 +1,5 @@
-Sellsy Client Library
-=======================
+Sellsy API Client Library
+=========================
 
 [![Build Status](https://travis-ci.org/ferjul17/Sellsy-api.svg?branch=master)](https://travis-ci.org/ferjul17/Sellsy-api)
 [![Coverage Status](https://coveralls.io/repos/ferjul17/Sellsy-api/badge.svg?branch=master&service=github)](https://coveralls.io/github/ferjul17/Sellsy-api?branch=master)
@@ -18,3 +18,72 @@ $promise = $client->getService('Infos')->callAsync('getInfos', [])->then(functio
 });
 $promise->wait();
 ```
+
+How to install
+--------------
+
+First of all you need [Composer](https://getcomposer.org/doc/00-intro.md "Introduction - Composer"):
+
+    php -r "readfile('https://getcomposer.org/installer');" | php
+
+Then add Sellsy API as a dependency of your project:
+
+    php composer.phar require ferjul17/sellsy-api
+
+How to use
+----------
+
+The library provide you a class called `Service` which represent a part of the Sellsy's API.
+The service allows you to call api associated to this module.
+For instance, the service `Accountdatas` allows to call all method which start with Accountdatas in Sellsy's API, like Accountdatas.getTaxe or Accountdatas.updateUnit
+
+The Services are created by a factory called `Client`. So you first need to create a `Client` before having a `Service`.
+To create a client just call its constructor. Its first argument is an array which contains the configuration.
+You must provide the credentials to call the API which include the user token and secret, and the consumer token and secret that you can find in Sellsy interface.
+
+```php
+$client = new Client(['userToken'      => 'xxx', 'userSecret'     => 'xxx',
+                      'consumerToken'  => 'xxx', 'consumerSecret' => 'xxx',
+                     ]);
+```
+
+Once you have you client, you can retreive a `Service` by calling the method `getService($serviceName)`:
+
+```php
+$service = $client->getService('Accountdatas');
+```
+
+Finally, you can call an API with the method `call($methodName, $params)`:
+
+```php
+$response = $service->call('createUnit', ['unit' => ['value' => 'Kg']);
+```
+
+There's another method `callAsync($methodName, $params)` which send an asynchronous request and return a `Promise`:
+
+```php
+$promise = $service->callAsync('createUnit', ['unit' => ['value' => 'Kg']);
+$response = $promise->wait();
+```
+
+You can find more information about `Promise` [here](https://github.com/guzzle/promises "Github of Guzzle Promises").
+
+How to run tests
+----------------
+
+If you want to test this library, you can run the test suite clone this repository:
+
+     git clone https://github.com/ferjul17/Sellsy-api.git
+     
+then install dependencies:
+
+    composer update
+
+than run the tests:
+
+    vendor/phpunit/phpunit/phpunit
+
+License
+-------
+
+Sellsy API is an open-source project released under the MIT license. See the `LICENSE` file for more information.