Update with usage instructions

Signed-off-by: camille-bouvy-frequenz <camille.bouvy@frequenz.com>

README.md

@@ -7,6 +7,12 @@
 ## Introduction
 
 Electricity Trading API client for Python
+The Frequenz Electricity Trading API client for Python is an easy-to-use Python interface built to interact with the Frequenz Electricity Trading API. It allows you to create orders, get market data, and manage your orders.
+
+## Features
+* **Create and manage gridpool orders**: Place new orders, update existing ones, and cancel orders when necessary.
+* **Stream live data**: Get real-time updates on market data, including order books, trades, and market prices.
+* **Retrieve historical data**: Access historical data on market trades.
 
 ## Supported Platforms
 
@@ -16,6 +22,101 @@ The following platforms are officially supported (tested):
 - **Operating System:** Ubuntu Linux 20.04
 - **Architectures:** amd64, arm64
 
+## Usage
+
+### Installation
+
+You can install the Frequenz Electricity Trading API client via pip. Replace `VERSION` with the specific version you wish to install.
+
+```
+# Choose the version you want to install
+VERSION=0.1.0
+pip install frequenz-client-electricity-trading==$VERSION
+```
+
+### Initialization
+
+First, initialize the client with the appropriate server URL and API key.
+```python
+from frequenz.client.electricity_trading import Client
+
+# Change server address if needed
+SERVICE_URL = "electricity-trading-testing.api.frequenz.com:443"
+API_KEY = open('api_key.txt').read().strip()
+client = Client(
+    server_url=SERVICE_URL,
+    auth_key=API_KEY
+)
+```
+
+### Create an Order
+
+Here's an example of how one can create a limit order to buy energy.
+```python
+from frequenz.client.electricity_trading import (
+    Currency,
+    DeliveryArea,
+    DeliveryPeriod,
+    Energy,
+    EnergyMarketCodeType,
+    MarketSide,
+    OrderType,
+    Price,
+)
+from datetime import datetime, timedelta
+from decimal import Decimal
+
+# Define order parameters
+gridpool_id = 1
+delivery_area = DeliveryArea(
+    code="10YDE-EON------1", # TenneT
+    code_type=EnergyMarketCodeType.EUROPE_EIC
+)
+delivery_period = DeliveryPeriod(
+    start=datetime.fromisoformat("2024-05-01T00:00:00"),
+    duration=datetime.timedelta(minutes=15)
+)
+price = Price(amount=Decimal("50.0"), currency=Currency.EUR)
+quantity = Energy(mwh=Decimal("0.1"))
+order = await client.create_gridpool_order(
+    gridpool_id=gridpool_id,
+    delivery_area=delivery_area,
+    delivery_period=delivery_period,
+    order_type=OrderType.LIMIT,
+    side=MarketSide.BUY,
+    price=quantity,
+    quantity=quantity,
+)
+```
+
+### List Orders for a Gridpool
+
+Orders for a given gridpool can be listed using various filters.
+
+```python
+from frequenz.client.electricity_trading import MarketSide
+
+# List all orders for a given gridpool
+orders = await self._client.list_gridpool_orders(
+    gridpool_id=gridpool_id,
+)
+
+# List only the buy orders for a given gridpool
+buy_orders = await self._client.list_gridpool_orders(
+    gridpool_id=gridpool_id,
+    side=MarketSide.BUY,
+)
+```
+
+### Streaming Public Trades
+
+To get real-time updates on market trades, one can use the following code snippet.
+
+```python
+async for order_detail in client.stream_public_trades():
+    print(f"Received public trade trade: {order_detail}")
+```
+
 ## Contributing
 
 If you want to know how to build this project and contribute to it, please