To move a card to the foundation simply double tap on the card you want to move. If there is a legal place on the foundation the card gets automatically moved there.
Alternatively you can of course drag the card manually to the foundation. But please keep in mind that the destination stack will be determined based on the point where you lift your finger and not relative to the place, where the card is drawn.
Towards the end of a game you often have to move a lot of cards to the foundation - one after the other. To simplify that task call the function "clean up" from the game menu.
this will move as many cards to the foundation as possible.