when i adopted two kittens from the shelter, i learned two things:

1) do not rush them. humans are literal giants to cats. their whole life has been turned upside down at this point. let them take their time when they are discovering everything because literally everything is new to them now.

2) this is their new home. reassure them that this is a safe place. keep the doors open so they can roam around. have enough fresh water and food and a clean litter box available at all times. do not disturb them when they are sleeping, eating or taking care of themselves.

keep in mind that they are tiny creatures in a very big world. they will approach you when they feel ready.