working on czml.html and i am trying to put obstacle by my own, how can i do it?

Link :

I would recommend you read over the Visualizing Spatial Data tutorial, which should give you a good overview of working with the Entity API. Then I would check out the Sandcastle Interpolation demo, which shows how to programatically create a time-dynamic moving object.

If you would rather work with CZML files instead of JavaScript, then I would start with the CZML Guide and use the vehicle.czml example that ships with Cesium to get you started.