How to create database diagram of a database in SQL Server

i have created a database in sql server. Now i want to create a database diagram to make relationship among tables. but whenever i click of database diagram option then this following error开发者_Go百科 is occured. Please suggest me what should i do ?

Please read the message carefully. It states that diagrams cannot be added to a database if it doesn't have a valid login as owner. You can change it on the Files page of the properties dialog of the database (right click and choose properties on the DB). Set the owner to any valid login and diagrams will be enabled.