Update README

Author: ciniml

README.md

@@ -1,10 +1,52 @@
-# WireGuard Implementation for ESP-IDF
+# WireGuard Implementation for ESP32 Arduino
 
-This is an implementation of the [WireGuard®](https://www.wireguard.com/) for ESP-IDF.
+This is an implementation of the [WireGuard®](https://www.wireguard.com/) for ESP32 Arduino.
 
-Almost all of this code is based on the [WireGuard Implementation for lwIP](https://github.com/smartalock/wireguard-lwip), but some potion of the code is adjusted to build with ESP- to run on ESP32 devices.
+Almost all of this code is based on the [WireGuard Implementation for lwIP](https://github.com/smartalock/wireguard-lwip), but some potion of the code is adjusted to build with ESP32 Arduino.
 
-# License
+## How to use 
+
+1. Include `WireGuard.hpp` at the early part of the sketch.
+
+```c++
+#include <WireGuard.hpp>
+```
+
+2. Define the instance of the `WireGuard` class at module level.
+
+```c++
+static WireGuard wg;
+```
+
+3. Connect to WiFi AP by using `WiFi` class.
+
+```c++
+WiFi.begin(ssid, password);
+while( !WiFi.isConnected() ) {
+    delay(1000);
+}
+```
+
+4. Sync the system time via NTP.
+
+```c++
+configTime(9 * 60 * 60, 0, "ntp.jst.mfeed.ad.jp", "ntp.nict.jp", "time.google.com");
+```
+
+5. Start the WireGuard interface.
+
+```c++
+wg.begin(
+    local_ip,           // IP address of the local interface
+    private_key,        // Private key of the local interface
+    endpoint_address,   // Address of the endpoint peer.
+    public_key,         // Public key of the endpoint peer.
+    endpoint_port);     // Port pf the endpoint peer.
+```
+
+You can see an example sketch `uptime_post.ino`, which connects SORACOM Arc WireGuard endpoint and post uptime to SORACOM Harvest via WireGuard connection.
+
+## License
 
 The original WireGuard implementation for lwIP is licensed under BSD 3 clause license so the code in this repository also licensed under the same license.