Hi, how can I add all cards from the 4 decks to my collection, is there an easy way to do this quickly?

Thanks

Check out the resource thread I created here. It links to CSV files for a lot of the preconstrcuted products Wizards has put out. Or if you just want to get right to C19, here's a direct link to a CSV for all 4 decks. Just download the CSV file, go to Inventory, click "Add Cards", then "From a CSV File". The CSV will not replace your existing inventory; instead, it'll just add the new cards to it.