Read over the description of the free stuff. There may be pictures of the free stuff as well.
If you'd like to get the Craigslist stuff for free, you'll need to contact the person who is giving it away. They may want you to call or email so follow whatever directions they want you to do.
If the description doesn't state how to contact the person giving away the free stuff, click on the email address near the top of the page to email them.