To add a class to My Queue, follow these steps:
Go to the video page of the class you want to add to your queue. Below the video player, click the + Queue button. There is also an x in the upper right corner of each video in your playlists, if you wish to remove a video. This x option will also pop up next to the word "Watchlist", within a green bar, once you add the video
To view your Queue, go to [Your Name]>Queue.
In this view, you can change the order of the classes in the playlist by clicking the Re-Order Playlist button.
Finding My Queue on the Mobile App
In the menu, go to the My Videos section > My Queue.
If on a mobile web browser, your Queue can be found under the Main Menu > Account.