The way it works on ThemeForest (click here to view the bundled plugin docs on their site) is when a premium plugin (sold on Codecanyon) is included for free with a WordPress Theme you can use the plugin without any issues, however, if you want automatic updates and support from the plugin developer you need to purchase it separately (this is 100% optional). Some plugins include a field to enter your “purchase” code for the plugin. Since you purchased a bundled product you do NOT have a purchase code for that plugin so you can’t enter anything in this field. Updates to the plugins are provided when the theme itself is updated as mentioned on the documentation section regarding updates.
If you have any issues with one of the bundled plugins you should contact us (the theme developer) for assistance, unless you have purchased your own license of the plugin in which case you can forward any queries to the plugin developer.