How to create a database diagram (Enterprise Manager)

To create a database diagram

Expand a server group; then expand a server.
Expand Databases; then expand the database in which to create the database diagram.
Right-click Diagrams; then click New Database Diagram....
The Create Diagram Wizard guides you through the process of creating a database diagram.

Creating and Managing Database Diagrams	How to insert a new table into a diagram
How to add an existing table to a database diagram