For this one, recommend starting with the HoloLens 1 developer samples here:
[https://video2.skills-academy.com/en-us/windows/mixed-reality/develop/unity/tutorials/holograms-100](https://video2.skills-academy.com/en-us/windows/mixed-reality/develop/unity/tutorials/holograms-100)
This should help get you started for the question above with sample codes.