This page is a resource resulting from this Deckbox forum post.

Download CSV files for preconstructed decks from the lists above, then go to Inventory > Add Cards > From a CSV File and import the deck. Note that this will add to your inventory rather than replace your inventory.

Note what cards each CSV contains prior to importing, in case you would like to edit the CSV first (e.g. split up a Duel Deck with a friend, change tokens from double-sided to single-sided, remove the basic lands, etc.).