To register your website in Yahoo for free, follow these steps:

1. Go to https://search.yahoo.com/info/submit.html.

2. Type in the URL of your website into the field provided.

3. Type in the email address associated with your website.

4. Type in the verification code displayed at the bottom.

5. Click on "Submit your Site".

Once you've submitted your website, it will be reviewed by the Yahoo search team. It can take a few weeks for your website to be indexed and show up in Yahoo's search results. It's also a good idea to make sure your website is optimized for search engines, using relevant keywords and high-quality content.