Show prefab/GO in viewport via script

Hi All,

Let's say i have a folder in project view in Editor, i have some imported OBJ geometry, textures etc. in this folder. If i want to see GO from this folder in Editor's viewport (Scene), i have to drag it into the scene or into the hierarchy view. This is exactly what i need, but via script, not manually! Of course i have my GO already stored in variable inside my script, but what should i use to send it to the scene?

Thanks in advance for your answers!