To import into your scene go to File>Append, navigate to .blend files folder, open the file, open "Group" folder, then double-click on the name of the group and append.

The name of the model and the name of the group is the same.

Milton Chair_3Dshaker

Or you can select it and copy it u sing CTRL+C and in your scene pressing CTRL+V.

Please note that this scene contains textures from ALEXANDER - Textures may not be redistributed

HDRI maps are from HDRI Haven