Update README.md

Author: LavanyaA

README.md

@@ -1,2 +1,17 @@
-# tooltip-customization-flutter-chart
-Customize the tooltip in Flutter Cartesian charts
+# Tooltip customization in flutter chart
+
+Flutter Cartesian chart widget provides support for customizing the tooltip in the chart using the callback events on rendering. Callback events are callback function or a method, which you pass as an argument into another function or method and can perform an action when you require it. Likewise, the chart widget provides a callback event called onTooltipRender to customize the tooltip contents as required.
+
+Documentation: https://help.syncfusion.com/flutter/cartesian-charts/callbacks#ontooltiprender 
+
+## Requirements to run the demo
+* [VS Code](https://code.visualstudio.com/download)
+* [Flutter SDK v2.0.0+](https://flutter.dev/docs/development/tools/sdk/overview)
+* [For more development tools](https://flutter.dev/docs/development/tools/devtools/overview)
+
+## How to run this application
+To run this application, you need to first clone or download the ‘tooltip customization flutter chart’ repository and open it in your preferred IDE. Then, build and run your project to view the output.
+
+## Further help
+For more help, check the [Syncfusion Flutter documentation](https://help.syncfusion.com/flutter/introduction/overview), or
+ [Flutter documentation](https://flutter.dev/docs/get-started/install).