Clicking on the stock will transfer one card to each of the tableaux stacks, if all spaces in the tableaux have been filled.
Foundation (8 stacks). Single cards cannot be moved to the foundation. Only when you have constructed a complete sequence on the tableau, 13 cards in sequence from King to Ace, may you move it to the foundation.
Tableau (10 stacks). Build regardless of suit and down, e.g. a 9 goes on a 10. Move sequences in suit and down, e.g. a 9 goes on a 10. Any card may be placed in an empty tableau. Completed sequences of cards may be moved together.
Wikipedia