Hi,
simple RX|FIFO code can be found here
https://community.nxp.com/docs/DOC-335321
When preparing MB for TX or RX while RXFIFO is enabled be sure you write to correct MBs. For example if CTRL2[RFFN]=0, MBs 0 to 7 are used by RXFIFO engine.
If you want to receive all messages (assume all ID) clear mask acceptance registers, thus incoming ID will be don't care.
BR, Petr