update README

README.md

@@ -8,3 +8,40 @@ Install with
 ```
 npm install git+https://github.com/Nordstrom/metrics-client-node.git --save
 ```
+
+### Usage
+To get started, initialize a new instance with protocol.
+```js
+const MetricsClient = require('metrics-client-node')
+var client = new MetricsClient({
+      protocol: 'udp',
+      host: 'localhost',
+      port: 8092
+    })
+```
+Or to enable buffer
+```js
+const MetricsClient = require('metrics-client-node')
+var client = new MetricsClient({
+        protocol: 'http',
+        bufferEnabled: true,
+        host: metrics.lambda.uri,
+        port: +metrics.lambda.port,
+        database: metrics.influxdb,
+        maxBufferSize: +metrics.bufferSize,
+        flushInterval: +metrics.flushInterval
+    })
+```
+
+To send message(s)
+```js
+client.send(message)
+```
+
+To close the client
+```js
+client.close()
+```
+
+### Limitation
+We only support 2 protocols: http and udp; and udp is only default protocol.