Discard the lemon skins and pot up in hot sterilised jars and seal with lids immediately.
Store in a cool dry place and once opened store in fridge where it will last months. Jam is best eaten in 1st year but will last years if stored properly.
Sterilise jars by washing in hot soapy water or use fresh from the dishwasher, fill with boiling water, emptying and then place in oven for 20 minutes at 140°C leaving in oven until jam is ready. Washed lids should be sterilised with boiling water and then left to drain.