From the post creation flow, you can add an image to your post. If the post you want to submit is just an image without a link, click the Image icon just below the post Description.
The recommended image size is 640 x 420 pixels.
You'll be prompted to select a filed stored on your device. After selecting the file, a preview of the post image will be available in the post creation flow. You can click the X in the top-right of the image to remove it from the post. Then enter the post's Title. Additionally, you may be required to enter a post Category and Tag before clicking Submit.