Remove the pieces from the game and set up the correct stamps in the correct slots, which are arranged from high to low, in a left to right fashion. For example, each "ones" place stamp will have a "1" printed on top while "tenths" place values will have a "0.1" printed on the top.
Show the game to the children and explain what each stamp represents. Hold up the stamps for the hundreds, tens, ones, tenths and hundredth values. Point out the decimal on each of them.
Sit one of the children down and ask them to make a number using the stamps. For example, they could make "134.37" by pulling down one stamp from the hundreds value, three stamps from the tens value, four stamps from the ones value, three stamps from the tenths value and seven stamps from the hundredths value.
Guide them through the process, and correct them when necessary. Let each child have at least one turn creating numbers before moving to math problems. .
Put a large number on the game board, such as "134.37" and have the children perform math problems using it as a guide. For example, have them subtract "42.21" from their number. They would remove four tens stamps, two ones stamps, two tenths stamps and one hundredth stamp.
Give every child a chance to use the game to make math problems, or hand out multiple game copies for your students. Write math problems on the board for your children to solve and have them solve the problems only using the stamp game.