Click the icon or in the middle
The icon at the bottom left indicates that this picture is the main picture that would appear on the post. You may choose any picture as your main photo. However, you cannot re-arrange the sequence of the remaining pictures that you have uploaded.
Select image and click done & share
Describe the look section: Upon keying in the section, a drop down of #hashtags would appear for you to choose from.
You are also able create or add new hashtags if the hashtags are not available in the drop-down list.