The featured image is the picture that appears to the left of a post in a category/tag display page—the webpage with the headlines and first few lines of each of your posts. To add the image, choose “Add featured image”, the last selection in the right-hand menu of the Add New Post and Edit Post screens. Browse and select your image. Make sure to select “Use as featured image”, which is in plain text towards the bottom of the select media screen. Click “Save All Changes” and then Update or Publish. The best size for your featured image is 150 X 150 pixels.