Updating Elements While Updating a Template Created in the Open DGN File

Open the DGN file in which the template was created and stored.
Open the Element Templates dialog (Drawing > Home > Attributes > Element Templates > Manage).
Select the template you want to change.
In the Properties pane, change properties associated with this template.
Elements in the DGN file that are associated with this template and that use these properties are resymbolized automatically.