Click on the info button to see the goal arrangement. Press space, or click the grey button in the top right corner, to pick up a card from the draw pile. Then move the card to a yellow space and click to place it. Cards cannot be moved once placed. However, when all yellow spaces are filled, you can remove tens and pairs of cards that add up to ten by clicking on them.
I learnt this game from some book that we borrowed from the library a long, long time ago... If you are lucky enough to have a complete deck, I honestly recommend that you play the game with real cards rather than a computer!