Cooking them by any method will make them softer (how soft depends on cooking method/duration) but will not make them riper/sweeter.
If when you smell them now they have a peach aroma you can do one of a few things: Peel them and poach them in a simple syrup (sugar and water; sugar, water and a vinegar; sugar and wine, etc., spiced or not) till cooked through; peel them and slice or chunk them and skewer them, grill over moderate heat, basting with one of the syrups (include some butter in it); or peel them and grate them, cook them in a little butter till soft then add to a Q sauce.
If when you smell them now they are not peach-y they will not become peach-y during cooking (and possibly won't become peach-y at all).
Here, however, is something you can do with hard peaches:
Unripe Peach Slaw
4-5 unripe peaches, peeled, sliced thinly (avoiding the pit), then cut in a julienne
1/2 c plain yogurt
2-3 t honey (start with 2)
2 T fresh lemon juice
1/4 t ground ginger (or a little freshly grated)
pinch ground allspice
salt and pepper to taste
Combine all and fridge for several hours or overnight.