Q.ripening nectarines
Can I ripen nectarines if not fully matured, but the branch broke? Moved here 6/14. Tree had leaves only. This year bloomed and got round fruit. No nursery or tree service could tell me what kind of tree it was, so didn’t know how to care for it. Again 6/1/15, went to 2 nurseries and had arborist here for other problem and they ALL told me it was a nectarine! But now it’s loaded and heavy fruit and I assume the fruit will increase in size. I used rope and twine to hold up some of the very heavy branches. The arborist said I should trim out some of it. I did..but with a wind yesterday 3 unsupported BRANCHES SNAPPED (2 lg, 1sm)! I propped up 2 lower to the ground ones. How do I save the fruit on them? Can I? (i.e. like grocery stores do when they ship from other countries) I put ends in bucket of water and put duct tape around broken part on tree. Don’t know if that’s right either. Please help–I hate to lose all this fruit, especially now that I know what it is.

I'm sorry that some of the branches on your nectarine tree broke, but how awesome that it's producing all that fruit for you! You may not be able to save all the fruit, but these articles may help you get started on at least trying(the first one describes ripening indoors):
https://www.gardeningknowhow.com/edible/fruits/nectarines/picking-nectarines.htm
https://www.gardeningknowhow.com/edible/fruits/nectarines/growing-nectarine-fruit-trees.htm
https://www.gardeningknowhow.com/edible/fruits/nectarines/how-to-thin-nectarines.htm
As for the broken branches on your tree, there's only a very small chance the fruit is actually mature enough to pick and let ripen indoors, but you can certainly try. Instead of duct tape around the tree, try plant tape or old pieces of nylon to help hold the broken areas together. Again: no guarantees, but it's worth a try. These articles may help you:
https://www.gardeningknowhow.com/garden-how-to/info/reattaching-broken-stems.htm
https://www.gardeningknowhow.com/ornamental/trees/tgen/wound-dressing-on-trees.htm
https://www.gardeningknowhow.com/plant-problems/environmental/wind-injury-to-plants.htm