No active material selected to add node group Help!

Hello, I’m pretty much new to Blender, even this question might sound silly. So I just designed a sofa (watching Blender Guru’s tutorials by the way)

So in that video he teaches about adding texture to the object (like the cushions). We had to download a texture from Poligon, and also I installed the Poligon material add on for Blender. Then in the video, he adds the material by navigating in the files, i did the same too Then he switched to some window pressing Shift + F3, and there he had the node groups already setup by the Poligon add on. I did not have anything similar, mine was empty. I tried pressing Shift + A and then selecting the Poligon group menu, but I had no luck.
It says that “no active material selected to add node group” in
orange highlight.

The one thing I cannot understand is, how did Blender guru have the nodes already set up by the Poligon add on while my one hadn’t, and even I cannot do it? I’m new, so there must be some mistake.

Thanks in advance.

In your screenshot your right area is in the “compositor” editor. You need to select the “shader editor” which he hovers over shortly in the drop down menu at 5:53 in the video.

Blenders interface is separated by “areas” that you can adjust, split or join.
You can change the editor of every area to your needs my pressing the symbol in the top left of each area (it could also be in the bottom left, if the header of that area was set to it by right klicking it)

There are multiple editors bound to shift+F3, you most likely pressed it 2 times without noticing.

Yes, that’s what happened. There are several editors for the Shift + F3 shortcut. Thanks.