Delete Archive log file
Deleting archivelog data would normally be done as part of the backup operation removing older archive data after a new backup is taken.

You should read the following:


Oracle Concepts Guide (pdf), particularly chapter 11
Administrator's Guide, chapter 13 (which has useful information on Archive Logs).


Only after reading all that should you look at the Backup and Recovery guides section on Configuring an Archived Redo Log Deletion Policy. I purposely did not provide a direct link.  When you are ready, you can lookup the book in the Master Book List.