Applies to Oracle 10g and above

I would assume your database is already in the ARCHIVELOG mode

SQL> show parameter LOG_ARCHIVE_DEST

This would show all your Archive Log Destinations without any value unless previously set. It would be wise to set multiple Archive Log Destinations on alternate physical disks. It would prevent the database to stop functioning if the first destination disk is full.

SQL> alter system set LOG_ARCHIVE_DEST_1='LOCATION=E:\BACKUPFOLDER'

The LOCATION keyword is used to define that the destination is local; for remote destinations use the keyword SERVICE

SQL> alter system set LOG_ARCHIVE_DEST_2='SERVICE=yournetworkservicename'