Gentle dry or moist heat helps soften the plastic and remove the wrinkles. For minor wrinkles, you can use a hairdryer on a low setting. Run the hairdryer back and forth over the wrinkles and smooth them out with your hand. Another option is to hang the tablecloth on a clothesline for a full day when the weather is warm or hot. The third option that works well for vinyl tablecloths is to use an iron on low heat in combination with a thick damp bath towel, making sure no part of the iron is ever placed directly on the plastic. Check if the crease is gone and repeat once if necessary. Iron out the creases one by one and spray more water on the towel to keep it damp.