Go to File → Append

Look for the file that contains the materials and double click on it

Go to the NodeTree folder

Select the Node tree and click on "Append"

Now you can assign the texture by clicking on "Background" and select the "group" in "World properties" panel.

Go to File → Append

Look for the file that contains the materials and double click on it

Go to the material folder

Select the material and click on "Append"

Now you can assign the material to your object and customize it in the "material properties" panel or in the Shading workspace.