To Add Template 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.

A cascading submenu of property categories and properties appears.
Select a property.
The selected property appears in the Properties pane under the name of its category. If the selected property is not visible in the Properties pane, click the downward pointing arrow on the right side of the property's tab.
(Optional) To add multiple instances of the same property, in the Properties pane right-click the property and select Add <property>.
(Optional) To add other properties from the same category, in the Properties pane right-click its tab and select Add <property>.
The selected property appears in the Properties pane on its tab.
Do one of the following:

For each added property, click the downward pointing triangle to the right of its name and select a value for the property.

or
Select the existing value and type a new value.