Any flashcard you want to export, open it, then select the More menu (three dots) right below your profile icon on the upper, right corner.
Click Export to download a .csv file of the flashcard/ deck, with Terms in one column and Definitions in the second one.
Keep in mind that images and special formatting won’t survive the import. Also, avoid special characters in the title - those might cause errors.
Lastly, you can re-import the .csv file back to StudyBlue, even after making changes to it.