Hey :)
I usually set the kitten / kittens up in a play pen for a few days in a central part of my house with everything they need (food, water, toys, litter etc...) so that my cats can kind of see them from a distance and have the choice to go up to them in their own time and investigate through a barrier rather then having the kittens wandering into their space.
This way it's kind of more on your pet cats terms, and they can take their time!
I hope this helped a bit :)
#FosteringaPet