In Forty Thieves Solitaire the goal of the game is to move all the cards to the 8 foundation piles located in the upper right corner.
The foundation piles are built in suit in an ascending order from Ace to King. You can use the middle 10 piles to hold the cards temporarily while you build up the cards in the foundation piles.
You may only move one card at a time, and you can only move a card to another pile if it is one lower and in the same suit. If you cannot make a move you can turn over a new card by clicking on the facedown deck in the top left of the game screen.