The easiest way to search for a video on PBS.org is to use the keyword search feature located in the upper right side of the PBS.org website. If you want to see Nature's Soul of the Elephant, you can simply type "Nature Soul of the Elephant." You can use quotation marks around the title for more accurate results or, if you are not sure of the exact title, just type keywords.
If you are searching for a specific episode of a show, you can type the show name and season and episode number in the keyword search. For example, Poldark Season 1 Episode 2.