To start a virtual closet on Poshmark, you need merchandise from your own closet, shipping materials, and a mobile phone with a camera. You take pictures of your items to showcase in your online closet. Then you upload the pictures, describe each item, label it, and post it for sale. When an item sells, you print the shipping label provided by Poshmark, package the item, and drop it off to be shipped using the USPS Priority Mail boxes.