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.

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

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