To find your Deck Code from the game Elements, click the "Your Deck" button and then the "Import/Export" button.
To track your card collection, try the Elements Card Tracking spreadsheet on Google Drive.
To use dek.im quickly, try these two bookmarklets (drag one or both to your bookmarks bar):
Copy to dek.im
(Open deck code highlighted on page)
Prompt dek.im
(Open deck code via prompt)