Captions and keywords help people and search engines find your photos. You can edit images individually by clicking the file edit page (as below) or you can bulk edit files using the Collection toolbar on the edit collection page (My Images > then click on the collection name) page. If you have already added captions and keywords to your file metadata this will be extracted and added to the database during upload.
What sort of words should I add to my captions and keywords?
You should consider your captions and keywords carefully making sure your images will be shown in search results pages only when appropriate. Adding many unnecessary words is likely to make your images be displayed lower down the results, whereas not including relevant words will make the image not show up when it is appropriate. Image buyers find incorrect, misspelling and inaccurate keywords and captions annoying, and it ultimately wastes everyone's time.
Here is an example of the sort of quantity or words required for an image. The Caption is a simple sentence or two to describe the image, whereas the keywords are words that describe the image including a few words to include mood or emotion:
Caption: Loire River at Bouchemaine, Pay-de-la-Loire, France. Looking west at sunset from the bridge travelling into Bouchemaine town near Angers.
Keywords: Loire river, France, Nante, Angers, Bouchemaine, sunset, tranquil, peaceful, Europe, EU,
The collection name and the collection description help to describe the collection to the visitor and external search engines (Google and Bing etc) however the words in the name and description are not included in the index for the images inside the collection.