Unable to create Database Diagram

Question

Dear
I have a created a  database Players.mdf. In Players.mdf, I have created two tables a) Manufacturer b)Player.
The table Manufacturer contains a Primary key column named ManufacturerId. The table Player contains a column PlayerManufacturerId.
Now I want to make relation between these two tables. I want PlayerManufacturerId as a Foreign Key to ManufacturerId of Manufacturer Table.
When I click under the Players Database node, and select Database Diagram, I got the error Message 'No Permission to create Database Diagram. No dbo permission.
Please anyone can help me on this  ?
Thanks