If you want your brought cards to go to your deck, tick the box next to "Automatically add the cards I purchase in the Market to my deck." (Its located under "The Market allows players to buy and sell characters between them. To sell your characters, use the link available below each of your characters in My Collection. To improve your collection with additional packs of characters, just go to The Shop."
Anyway if you want to add cards to your deck Click on this link http://www.urban-rivals.com/en/collection/pro.php
Remember to click on "set as deck"