When I invite my child to the toilet, they get upset and run away, and won't sit on the seat. Where should we start to help them get used to it?

There may be a reason they dislike it, such as the height of the seat, the sound, the smell, or the uneasy feeling of having their feet dangle. Rather than rushing to have them go, try one thing at a time based on what bothers them: sitting briefly with clothes on, flushing only after they've stepped away, or stabilizing their body with a step stool and a toddler seat. Use pictures or cues to show "toilet → wash hands → all done," and if they get upset, it's fine to stop for the day. If there's strong fear, pain, or constipation, talk with a medical provider first.