Vijay, just to confirm are meaning to display the property value of a thing over a chart something like Time Series Chart, there are some charts available out of the box and additionally you can download an extension from ThingWorx Marketplace called Custom Chart Widgets
Could you confirm which type of chart you are using?
In general you'll need a service from that Thing which contains the property value you require to be displayed on the chart and then bind the output of that service to the chart and then you can select from the Chart's property which ones you'd like to be displayed and how. There's example available here in a video for Time Series Chart Widget
Similarly you should also see for all the other chart widgets.
Hope this helps.