The fastest way is to select and hold any title until a prompt appears with the option to Add to My List/Queue. Tap on Add to My List/Queue and the title will be added to the category labeled My List/Queue.
Another way is to select a title from the home screen and tap the Add to My List/Queue button located next to the play button on the titles' description screen. Afterward, you can go back to the Tubi home screen, scroll up to My List/Queue, and you’ll see the movie/TV show you just selected on this list.
The icon to the left of the Play button is the Add to My List/Queue button. To add a title to your list/queue, tap it while it displays the plus (+) sign.
Once you've added a title to your list/queue, it will appear like this. To remove the title from your list/queue, tap it while it is displaying the minus (-) sign.