How to Release Wrinkles from a Velvet Pillow Cover
If your velvet pillow cover has any creases or wrinkles, turn it inside out, hang it from the edges and run through it with a fabric steamer using slow vertical strokes. Once done steaming, carefully turn the pillow cover right side out and the creases should be gone.
If you don't have a steamer, you can alternatively, very carefully, use an iron. Just make sure your ironing surface is completely flat and untextured so as not create new marks on the the pillow fabric.