To Add Material Properties

In the Element Templates dialog ( Drawing > Home > Attributes > Element Template > Manage ), expand the open DGN file and the template group.
Select the template to which you want to add properties.
Do one of the following:

Right-click the template to which you want to add properties and select Add from the pop-up menu.

or
Right-click below the existing properties in the right pane and select Add from the pop-up menu.
Select the Material property.
The Material property appears in the Properties pane. If the Material property is not visible, click the downward pointing arrow on the right side of the property's tab.
Click the arrow to the right of the Material field.
A drop-down window appears in which you can select a palette and a material.
Select a palette from the list.
(Optional) Do one of the following:

Click the first icon to the right of the Palette list to view images of the materials.

or
Click the second icon to view a list of the materials.

or
Click the third icon to delete the selected material.
Select a material.