soak it in water, Hang dry. You can use tumble dryer but it couldl fuzz the knits. Although probably not on the first time. I have washed and dried mine several times. If you have extreme wrinkles you probably will want to machine dry at least a bit, or they may not come out.
I did what @Skyhawk did. I will wet thoroughly with a spray bottle. Wife sometimes finds a good, mild fragrance that can be added if it has smells. Hang dry and repeat. I have also washed one on cold using the = of Woolite for colors. Hang and it looks new.
In my experience the best way would be just wear the jacket a lot, that way will make disappear the wrinkles naturally... dry cleaning won’t do much really and it’s very expensive (probably would be cheaper to buy another without wrinkles instead of trying to get rid of them with dry clean process at least in US) and ironing (DO NOT) will leave permanent shiny marks on the jacket, as the nomex helps to stop combustion process, as soon as the heat source is removed, gives you extra seconds, but the fabric will change it’s properties. (Not that pilots will care about how the jacket looks after an accident).
Just wear it all time and they will disappear!
I've run all of mine through the washing machine (cool temp, gentle cycle) and hung them up on hangers to drip dry. I smooth them out right after I hang them up and once they dry (by next morning for 36/P jackets) they have no wrinkles.