I would have thought it was a little late to make quince jelly for this year; made mine back in early October, but anyway this is what I do.
Wash however many quinces you have to remove the 'furry' coating then chop roughly into 2" pieces, no need to peel or remove seeds.
Put into a saucepan and just cover with water and bring to boil, simmer gently till soft. I usually use a pressure cooker and do them for 10 mins.
When soft mash them up then tip the contents into a tea towel lined mixing bowl. Suspend the tea towel above the bowl (I usually tie with string and hang it off a wall cupboard handle!) and allow the juice to drip into the bowl.
For every pint of juice add 1lb sugar and boil in the usual way to make jam. I add a juice of a lemon to assist in setting. The colour is a beautiful crimson red and quince jelly tastes divine on hot buttered toast or with roast lamb or cheese and biscuits.
Enjoy!