How should we add an object into the map using the coordinates

1. A concise explanation of the problem you're experiencing.
How should we add an object into the map using the coordinates?
Where should we add it?

2. Context. Why do you need to do this? We might know a better way to accomplish your goal.
I desire to study it.

3. The Cesium version you're using, your operating system and browser.
Last.

Do you mean if you have longitude and latitude coordinates, how to place an object on the map? This example creates some polygons based on these cartographic coordinates:

You might also find this workshop tutorial useful:

Especially the loading and styling entities section.