Your are posting ad in guest mode, create an account to get greater access, like modify ad, delete ad, save ad, tracking your payment etc.
70-100 character will be great title
A description will help user to know details about your product
Add youtube or vimeo url, ex. https://www.youtube.com/watch?v=video_id
These feature only for modern theme, if you set any video, then feature image will be disable in ad details page
Address line will help buyer to know about your location more specifically