Which model?
I've done a few XFC3A06001
Some ncis are cryptic (used for offsetting of AIs, setting AI type, etc) - so you'll want to configure the device in CARE via the plugin, download from CARE, then learn the device in AX.
There's no wizard written for these in AX.
The XFCs use standard snvt switches for all of the DIs and DOs, so you may want to do some logic to write to both value and state proxy points.
For example, for each DO I create a boolean writable point and link it to a:
numeric switch (false = 0, true = 100) -> value proxy point (numeric writable)
enum switch (false = 0, true = 1) -> state proxy point (enum writable)