update README.md

Author: mrt1m

README.md

@@ -4,7 +4,15 @@
 
 * PHP 7.4 or later
 
-## 2. Initialization
+## 2. Installation
+
+The VK PHP SDK can be installed using Composer by running the following command:
+
+```sh
+composer require mrt1m/playstation-store-ap
+```
+
+## 3. Initialization
 
 Create Client object using the following code:
 
@@ -15,9 +23,9 @@ use PlaystationStoreApi\Enum\Regions;
 $clientApi = new Client(new Regions(Regions::RUSSIA));
 ```
 
-## 3. API Requests
+## 4. API Requests
 
-### 3.1. Request product data
+### 4.1. Request product data
 
 ```php
 $response = $clientApi->product()->get('EP0001-CUSA12042_00-GAME000000000000');