from Microsoft TechNet:
To create a linked server to access a SQL Server database
Execute sp_addlinkedserver to create the linked server, specifying SQLOLEDB as provider_name, and the network name of the server running the remote instance of SQL Server as data_source.
For example, to create a linked server named LinkSQLSrvr that operates against the instance of SQL Server running on the server whose network name is NetSQLSrvr, execute:
sp_addlinkedserver N' LinkSQLSrvr' , ' ' , N' SQLOLEDB' , N' NetSQLSrvr'
Map each local SQL Server login that needs access to the linked server to a SQL Server Authentication login on the linked server.
This example maps access for the local login Joe to the SQL Server Authentication login Visitor on the linked server named LinkedSQLSrvr.
sp_addlinkedsrvlogin N' LinkSQLSrvr' , false, N' Joe' , N' Visitor' , N' VisitorPwd'
