These are not official Quizlet apps. Rather, they are by third-party developers and are powered by the Quizlet API.
If you have any issues, you'll need to contact the app developer directly, as Quizlet has no control over these apps.
Go to the section called "My Sets" (or similar sounding name) and all of your created and favorited sets will be listed there. Even sets from groups you've joined too!
You only need to connect your account once, and it's pretty quick:
Find the "login" or "login into Quizlet" button in the app. This should take you to the web browser (Safari) with a Quizlet login screen.
Once logged in, the next screen will ask if you want to trust this application. If you do, press "Allow".
You will be sent back automatically, already logged in!
How do I download my flashcard sets onto my iPad?
Each app is a little different, but the basic procedure is the same:
Make sure your sets are marked as publicly accessible (not private or shared only with a group)
Find on the application where you can do a search by creator for your username.
Some applications make you tap a "search" icon first, and then choose "creator" or "username".
Others have a separate screen outside of search.
Enter your username or the username of the set's creator.