You can add flashcards to an existing list or create a new list with specific words by following the steps below:
First, touch the word you want to add to a flashcard list:
Then, touch "Add to" in the upper right-hand corner of the screen. If you've never added a flashcard this way before, the screen will provide a prompt.
Next, choose the list you want to add the flashcard to, or click the Plus sign or "New Flashcard Set" to make a brand-new list of specific words you want to study.
You can also add any vocabulary word by tapping on it directly from the subtitles while you're watching a video or listening to an audio. If you do this with all the unfamiliar words you come across, you'll build a library of words you can study on a regular basis until you've mastered them.