You roll the 12 sided white die and then the 5 coloured dice. The object of the game is to try to make the number on the 12 sided die using a combination of the numbers on the coloured dice. You then move your counter according to how many dice you used - so if you used 3 dice to get to the target number, you move 3 spaces (therefore it is better to use as many dice as possible to make your sum as you get to move more spaces). The other player then gets a chance to make the target number using the remaining dice.
You can also use multiplication and division with children who can do this, or play together, trying to make as many combinations as possible to get to the target number, so I think these will be useful for some time.