If you are familiar with logging into yahoo that will not take more than a minute so make sure that you are logged in.
As you will access to your Yahoo mail account, you will see the there is a message in your inbox sent by someone.
Upon clicking on the inbox, the email will open showing the name of sender and subject. Look for the attachment button as indicated in the image and click on the button.
After clicking on the attachment button, you will be asked for a few options as mentioned in the image. You can see images, download them or can have a slide show.
If you will click any of the buttons, you will have the pictures displayed on your computer screen as shown in the image.