You'd have to get familiar with the BACKUP command.
a. FULL Backup (which is not part of an Incremental Backup Strategy)
b. INCREMENTAL LEVEL 0 Backup (which is part of an Incremental Backup Strategy)
c. INCREMENTAL LEVEL 1 CUMULATIVE Backup
d. INCREMENTAL LEVEL 1 DIFFERENTIAL Backup
You can script the RMAN backup and schedule it through DBMS_SCHEDULER or through Oracle Enterprise Manager or through an OS scheduler.
Hemant K Chitale