Check your website/domain on averyniceweb.com/appraisals (Open averyniceweb.com/appraisals home page and write your website/domain name then click "Calculate").
After an analysis and price calculation of your website, click "Sell my website/domain"
Site Verification page opens. Put the HTML code on your website main(root) page and enter the information that asked. And click "Verify" button. If verification done succesfully then fill out the form and your website/domain started to sell on averyniceweb.com/appraisals.