update README

README.md

 # QSI_Groupe4
 
-## Installation
+## Prerequisites
 
-To install dependencies, run the following command:
+Before you begin, make sure you have Node.js version 20 installed. We recommend using [Node Version Manager (NVM)](https://github.com/nvm-sh/nvm) for easy Node.js version management.
 
+```bash
+# Install NVM (Node Version Manager)
+curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.1/install.sh | bash
+
+# Reload the shell configuration
+source ~/.bashrc   # or source ~/.zshrc if you're using Zsh
+
+# Install Node.js 20
+nvm install 20
+
+# Set Node.js 20 as the default version
+nvm use 20
 ```
-npm install
-```
+
+## Installation
+
+1. Clone this repository:
+   ```bash
+   git clone https://gitlab.univ-lille.fr/lydia.tarmelit.etu/qsi_groupe4.git
+   ```
+
+2. Navigate to the project directory:
+   ```bash
+   cd qsi_groupe4
+   ```
+
+3. Install dependencies:
+   ```bash
+   npm install
+   ```
 
 ## Available Scripts
 
@@ -22,6 +49,14 @@ npm start main <filePath>
 
 Replace `<filePath>` with the path to your JSON file.
 
+Your json should contain the following content:
+
+```json
+{
+    "privateKey": "yourPrivateKey"
+}
+```
+
 ### `npm test`
 
 To run tests, use the following command: