Wash the area to clean it with warm water.
Put some vetericyn or triple antibiotic on it.
very gently with your pinky(gloves recommended) push the prolapse back in
slasher some raw honey on it and hold it as long as you can.
if it keep popping out you may need to go to a vet to get a stitch
you can also make a sugar flush to use every 2 hours to help with the swelling
sugar flush: boil water and add sugar until the sugar doesnt dissolve anymore. let cool and gentl use a little at a time to flush the inside of the vent every to hours. (vet recipe)
Sorry for your loss. A prolapse can be a common occurrence from a calcium deficiency, or straining to lay an egg or to poop. Make sure that your pullets and hens are on a layer feed or getting access to free choice crushed oyster shell. Once a prolapse occurs, the hen ahould be isolated since others will peck at and injure the vent and sometimes pull the intestines out. Here is a good article about prolapses: https://the-chicken-chick.com/prolapse-vent-causes-treatment-graphic/