Incremental backups are used with permanent journals. You need to enable journalling. These journals keep a snapshot of all the changes that have taken place since the last backup and while backing up, you just back up these journals rather than backing up the complete table or database.
The frequency for these backups can vary however a common practice is to have a daily incremental backup (journal only) and a weekly full backup (may be on weekends)
Refer to the documenation for more detail on journalling.