Hi Wenda:
The flexio interface is for Kinetis parts. Not sure this example has ported to i.mx RT .
The i.MX RT1050 processor has the special camera sensor interface (CSI) module, especially meant for parallel camera connection. So, there is no need of using FlexIO modules.
For the example of the CSI module use, please refer to the AN12110 Application note and the corresponding example, available on below link
https://www.nxp.com/docs/en/application-note/AN12110.pdf