I just created instructions for a faculty member who uses Quizlet so that she can integrate the flashcards within Canvas. There were resources in the Canvas Community about Quizlet along with other LTI's, but nothing (that I could find) that provided just the steps for using Quizlet. So, I thought I'd share them in case anyone else needs them along with my experience using the embed code:
1. Select Settings on the Course Navigation Menu
2. Choose the Apps tab
3. Search for Quizlet

4. Click the +Add App button to add the app to your course

5. Add a Content Page (to a Module) and select the "V" Icon to locate "Quizlet"

6. Search for any public flash cards (including your own) and select the Embed button
. 
7. Save the page.
Notes
Quizlet is free and also provides embed code that works really well within a Canvas page. However, when I tried it the game was the default rather than the flashcards. At first, I didn't realize that there is a drop-down to select specific embed code depending on whether you want: flashcards, match, learn, test or spell. However, the LTI seems easier to use for faculty members who are not familiar with the HTML view of the Rich Content Editor.