How do i configure flexcan mailboxes on Digi i.MX6UL boards

This can be a question which is more suited for freescale/NXP forums. But since i am having some issues logging in there, i am desperately reaching out to everywhere i can.
I know that the i.MX 6UltraLite supports Mailbox configuration for CAN Tx/Rx via Flexcan driver. But i have zero idea about how to access/configure the mailbox settings on flexcan. Any references like urls or documents is appreciated.

Thanks in advance.