It says to use those apertures when the subject is how far from the
flash?  Ten feet?  If so, the guide numbers would be 40 for ASA 100 and
56 for ASA 200.  Split the difference for ASA 160 and use 45-50.

Divide GN by distance for aperture.  Shutter speed is immaterial as far
as the flash exposure goes.

--
dadiOH
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you might want to go to the library and check out a book on photograph to
learn basics of exposure.   there might be classes at your local community
college, parks and rec, and there are chapters of the Photo Society of
America in most towns.

I believe you have a leaf shutter, (it opens all around at once, vs a
curtain that moves from one side to the other) so you can choose any shutter
speed that is appropriate.  AS the previous person said, the suggest
exposure is usally tied to a distance on a scale on the flash, unless you
have one with an auto exposure eye, then you could select an exposure you
prefer.

flash exposure is changed by the F/stop and output power
ambient light (room light) is changed by f/stop and shutter speed.

so you can select an exposure that will allow the room lights to keep up
with the flash,  that will allow you to expose with or without blurryness
from camera movement or subject movement by the many choices.

Oh, yeah, make sure the flash sync is set to X, if you have an M or other
settings on a switch, the other is for flash bulbs which must be fired a few
milli seconds before the shutter opens so the fire in the bulb can get a
head start, that would make the flash fire and disappear before the shutter
starts to open.

If none of the above makes makes any sense then go read up one basic
photography.

Sounds to me as though this is an automatic flash, so you set the
aperture for the ASA and it controls the exposure- no guide numbers
involved so long as you are within its distance range. I'd try
something between 4 and 5.6 for the Portra 160 and take a test roll.