Its simple really. Find cards you like, pick a strategy, put a deck together, test it against different types of decks and players, and edit it accordingly to make it better. If you find a deck online, be sure to edit it to fit your style of play.
If you are asking how you make a deck in the YVD program, SpiritofSteel, the owner of this site, made a video on his channel detailing it. Also there are help forums on the YVD main forums and website.