The issue:
To ship curtains they need to be folded so that they can ship in boxes. This of course will cause the material to have folds when it arrives and you unpack it. These wrinkles are more noticeable in the winter when temperatures are cold and the material is stiffer.
The Solution
These folds will relax overtime giving you a smooth curtain. How fast that happens depends on how warm your environment is and the size of your curtain. If you need to smooth the curtain out ASAP then you can use a hand held steamer.
Step 1 - Hang your curtains
Step 2 - Use a steamer on the medium-high setting and slowly move the steamer around the curtain.
WARNING: Do not hold it in one spot or you could warp/melt the PVC
Step 3 - Keep doing this over the entire curtain until the wrinkles have relaxed
Step 4 - Enjoy your curtain!