I dislike the new ads that appear on the right side of my email. Do I have to us

These are third-party and sponsor ads. You have to put up with them if you are using the free Yahoo! Mail service, and you have no paid subscription. This is how Yahoo! pays for your storage on their servers, with the money they receive from the companies in the ads. To get rid of them, simply upgrade to a paid version. This can be done by clicking Mail Upgrades on the top, right-hand corner of the mail viewer.