What you need are:
5 green apples
4 tablespoon of sugar
1/2 cup of lemon juice
Cut all the apples into dices
Heat the water (amount to be enough to cover the apples) with sugar
Put all the apples into the boiling water
Add in lemon juice
Keep stirring until all the apples turned soft and into thick sauce
Set aside the jam for cooling
Keep your jam in your favourite jars
Before that, prepare the jar by sterilizing with hot water
It's just that simple.
Try it and have fun!