Restore Oracle database from cold backup files
Cold backups, like hot backups can be taken in different ways. One is by using rman - recommended - the other is using OS tools like copy/dd. Next to that, storage based snapshots could be used. So in order to know how to restore, it is important to know how the backup has been made.

If the backup is properly made using RMAN, there is not much more to do than starting your instance, connect to the catalog, or find a snapshot controlfile that contains the backup administration, connect to the instance and issue a restore database command. If it is an OS tools backup, use the same tool[s] to copy the files to their original locations and start the database, once done.

There are many potential pitfalls using cold OS tool backups. I have seen situations in which the admin told me .... 


  'eventually we switched to xcopy because we got file locking problems
  ...'


instead of looking further. He missed the point that the database was started during the cold backup. This is one of my reasons not to be a big fan of COLD backups. They make me shiver.

Be smart and carefully read Oracle® Database Backup and Recovery User's Guide
11g Release 2 (11.2) It is worth every minute you spend studying it. Oracle backup and recovery is not hard, there are just a lot of options.