When you upload your picture, Ponga takes the image file title and converts it into the title for a picture making sensible changes. For example, "_" becomes a space, and Title Case is added so that "george_slaying_dragons.jpg" becomes "George Slaying Dragons." It's easy to change in a few clicks.
In most cases this will be a blank field at first. You add to it just by clicking in that area and typing. You can include up to about 1,000 characters in this field so feel free to use it for jotting notes and external links.
To change the title or description of a picture or album, you just mouse-over the title or description area, click, and just start typing.
You can also add a description the same way. Click in the description area and start typing. Currently the description can be up to 1000 characters and any included URLs will be auto-linked (you don't even need to include the protocol designator, or the "https://" in the link.)
Reach out if you have any questions.