Update README.md

Author: Hudo Assenco

README.md

@@ -1,3 +1,57 @@
 # react-optimize
 
-Integration with Google Optimize
+Integration with Google Optimize.
+
+Docs:
+ - Optimize Deploy with GTAG: https://support.google.com/optimize/answer/7513085
+ - Optimize JS API: https://support.google.com/optimize/answer/9059383
+
+
+## Instalation
+```
+yarn add react-optimize
+```
+
+## How to use
+You first need to add the gtag snippet with the optimize container id in it. If you are using [create-react-app](https://github.com/facebook/create-react-app)
+you can add the following to `public/index.html`
+```
+<script async src="https://www.googletagmanager.com/gtag/js?id=%REACT_APP_GA_ID%"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  gtag = function () { dataLayer.push(arguments); }
+  gtag('js', new Date());
+
+  gtag('config', '%REACT_APP_GA_ID%', { 'optimize_id': '%REACT_APP_OPTIMIZE_ID%'});
+</script>
+```
+
+and define them in your `.env`
+```
+REACT_APP_GA_ID=UA-xyz
+REACT_APP_OPTIMIZE_ID=GTM-abc
+```
+
+After that you can use the lib like the following:
+```
+import React from 'react';
+import { Experiment, Variant } from "react-optimize";
+
+class App extends React.Component {
+  render() {
+    return(
+      <Experiment id="<experiment-id>">
+        <Variant id="0">
+          Original
+        </Variant>
+        <Variant id="1">
+          Variant 1
+        </Variant>
+        <Variant id="2">
+          Variant 2
+        </Variant>
+      </Experiment>
+    )
+  }
+}
+```