Generally speaking limit distractions ( iPad /tv), have the meal prepared where they can eat It easily (cut and ready), and mix in foods they love with perhaps ones they love a little less to help set the pace. Portion control may also help- put less on the plate and then give more when finished. Eat with them so you can softly encourage it. Depending on the age because of motor skills and attention span this requires more patience. It’s better not to rush them too much when they are trying to adopt a skill like using a fork or knife.