how to add a material in solidworks 2013 premium?
If the material you need is not already there, you need to create a custom material.
From the manual:
Using a Custom Material
If the material you want to assign to the part is not in the SOLIDWORKS Material library, you can create a custom material. When you create a custom material, start with an existing material similar to the material you want to create.
To create a material:
In the Material dialog box, in the material tree, select the material on which to base the custom material.
Right-click and select Copy or press Ctrl + C.
In the material tree, select a category in a custom library. You can use the Custom Materials library or a library you created.
Right-click and select Paste or press Ctrl + V.
To rename the material, right-click the material and select Rename.
Edit properties of the material and click Save.