Hi! Welcome to the Cesium forum!
You're in luck - CesiumJS was created for just this sort of thing! Here's an example doing just that loading it from a CZML file:
You can see this file here:
CZML is an easy way to package time dynamic data and render it in CesiumJS. You could instead create this entity and point positions manually or with code inside your application.
Let me know if this helps!