I am using SimpleMembership (http://blog.osbornm.com/archive/2010/07/21/using-simplemembership-with-asp.net-webpages.aspx) but I am unable to have place my custom user table
Try this:
WebSecurity.InitializeDatabaseConnection(connectionStringName: "ApplicationServices", userTableName: "MySchema].[User", userIdColumn: "ID", userNameColumn: "Username", autoCreateTables: true);