The Configure Database Mirroring Security Wizard can be used to initially configure security settings at all or some server instances involved in mirroring. This wizard works in conjunction with the Mirroring page of the Database Properties dialog box.
To launch the Configure Database Mirroring Security Wizard
After connecting to the principal server instance, in Object Explorer, click the server name to expand the server tree.
Expand Databases, and select the database to be mirrored.
Right-click the database, select Tasks, and then click Mirror. This opens the Mirroring Page of the Database Properties dialog box.
Click Configure Security.