This game was made without mobile in mind, so it is probably only well playable on devices with a mouse and a big enough display.
Simply click with your left mouse to get a number. With right mouse you can make sure, that a left mouse click won't blow up a bomb.
The numbers on the field only display how many bombs are to their top, right, bottom and left.
As soon as you clicked on all fields without a mine (with your left mouse), you win.