You can purchase one ready-made, or make your own. Commercially produced compost bins are readily available. They are often enclosed so that flies can't get in and smells can't get out. This may be a consideration if your garden is small. The bins have an open bottom which needs to be in direct contact with the soil to assist with drainage and enable worms and other organisms to enter and help in the composting process.
Compost is easier to turn in larger bins.
A sprinkle of lime or dolomite over each layer helps to speed up the process. Old garbage bins and boxes can be adapted to perform a similar function. For a class project with many students involved, building a compost bin may be preferable. The compost itself can be made in a number of ways. The simple method, which produces usable compost in about 3 to 6 months, is to mix waste with a little soil and turning the compost with a garden fork every couple of weeks.