1.Connect to target Database with RMAN.
i)If you have lost your spfile while your database is running then,
ii)If your database is not up and you don't use recovery catalog then use,
2)Start the instance with dummy parameter file.
3) Restore server parameter file.
i) To restore in default location,
ii) To restore in another location,
iii) If you want to restore to a pfile then use,
4) Start the instance.