Remove the drum from your old washing machine. This process varies depending on the age, make and model of the machine. With some washers, for example, you may need to remove the plating on the outside of the washer to lift out the drum.
Saw off the rotation axis, if you wish. The rotation axis is typically like a metal spike that sticks out from the bottom of your drum -- you can either cut it off or drive it into the ground. To cut it off, saw through the spike at the base with a metal hand saw. Once you have cut through enough to break it off, whack it with a hammer to snap it.
Place the drum wherever you wish to grow and display plants. It is crucial to do this before filling it, as it will be too heavy to easily move once filled.
Fill the drum with soil and whatever plants you wish to grow.