kitten questions

my kittens r 3 wks old today, when do i have to introduce them to KRM and kitten food??? also when do i introduce them to a litter tray id say momma cat keeps eating it as ive seen nothing from any of them yet

Don't worry about it, just keep feeding canned and dry kitten food to the mom and she will teach the kittens when they're ready. Most will start trying solid food and using the litterbox at 4-5 weeks. They don't need KMR ever as long as they have their mother.