Important! Make sure that you have cycles selected as your render engine and your GPU selected as your device.

How To Append The Material

Open the File menu and click on Append.

Navigate to the folder where you downloaded the .Blend file. 

Double-click to open it.

Double-click on the folder name Material.

Double-click on the material named CRYSTAL GLASS, then click on Append.

Next, go to the shading tab and select the object you want to apply the shader to. Using the "browse-material" drop-down, select CRYSTAL GLASS from the list.

You should then see the nodes in the shader editor at the bottom of the screen. If you don't, move your cursor into the area and press A on your keyboard followed by the period button on your number pad to bring the node tree into focus.

Adjusting The Material

There are only three nodes that you need to worry about. 

Index of Refraction. You can look up different values online for different types of glass and precious stones but glass is usually somewhere between 1.4 and 1.9 although I do find a value of 2 works well.

Dispersion. It is unlikely that you will need to change this however 0.044 would be the default and you can go up or down in very minute amounts - 0.002 at a time. Small changes make a big difference here.

Glass Colour. If you choose to change this, make sure that the saturation value is low otherwise the IOR and dispersion will be cancelled out.