Very carefully !!!

Seriously,turn up the iron to the poly setting,JUST make sure you use a pressing cloth,and a damp pressing cloth would be better.Don't let the iron touch the poly,make sure it's totally covered with the pressing cloth.

If that doesn't work,totally wet them,and without wringing them out,hang them out on your clothesline.The weight of the water should make the wrinkles fall out as they are drying.HTH
Kathi

I used a similiar method to get the wrinkles out of my graduation gown. I was NOT wearing it looking like I'd slept in it :-0 I use a damp towel and, if I remember correctly, a little steam, being sure the iron did not come in contact with the material; also had to apply some pressure. It was a slow process, but it did take the wrinkles out. HTH

I've used a mixture of a small amount of vinegar in water with some success. Method same as above.

I swear by silk organza pressing cloths. Sheer enough to see what you're doing and will withstand high heat. Can also be used for interfacings. I've also used vinegar and water in a spray bottle with success both to set a crease and to remove one.

Mary

Thanks for everyone's suggestions--I knew I could count on GW folks! I have not yet had time to try any of these, but when I do I will let you know the results. CK