If you know the title of the video that you want, simply type it into the search box to see if we have it.
If you are more wanting to explore what videos might be available to you (instead of searching for a known item), then scroll down on the library's home page until you see (on the left) the quick link "Find a Video". Click on it.
The default screen lets you search for DVDs (and other video formats) in the library's catalog.
But if you click on the Streaming Video option, you will see list of all of the library's databases that contain streaming media. You can then click into the database that is of interest to you and see what kind of streaming video content is available.