The games Canfield, Klondike, and Double Klondike allow you to select either 1-card or 3-card draw from the stock. To set your preference, use the popup menu in the toolbar at the top of the game window.
Your selection must be made at the start of the current deal of the cards. Once you deal a card from the stock pile, you cannot change the draw preference for the game in progress until a New Game is selected.