You can change your word selection.  You can delete words from your Study List or Known List.  You can also move words between Study List and Known List.

From VocabularyShop Home Page click Select icon > click the drop down menu > select Saved

All words from your selection will be retrieved.  Words you selected for study will appear on the Study List, and words you put in Known List will appear on the Known List.  The Source List will be empty.  You can highlight words from either Study List or Known List then move them to the Source List.  You can also move words from Study List to Known List via Source List and vice versa.  When you click the Save button all words on the Source List will be removed from your word selection and any change you made will be saved.