Your child has come to a point where they can play independently and it is time for them to join their play with words. At first, they may be labeling objects they’re picking up or see. Let’s say they’re in their play kitchen and they say “banana”. You can expand on it by creating a phrase “Let’s PEEL the banana”. Emphasize novel words and unique parts of a phrase to allow it to stand out to your child.
It’s all about input they are receiving. The more verbal modeling that you provide during play, everyday errands, etc. the more likely they are to start narrating their own actions. Feel free to initiate structured play with them. For instance, grab a tea set and start setting it up by saying phrases such as “Here’s a plate”. Then, take the teapot and say “Pouring tea”, pretend to drink it and say “Drinking tea” or “Wow! It’s hot!”, etc.
Another alternative is to chime in when they have already initiated play with an item on their own. “Oh the car is going up up up the garage!”, “The car needs gas!”, “We’re driving fast!”, etc. They do not have to repeat everything you are saying, but you are giving their actions words and meaning. You are also adding new vocabulary to their repertoire. For example, they may already know “car”, but “gas” might be a new word. To give it extra meaning, talk about getting gas when you’re actually at the gas station. Real life situations will encourage them to make more connections and make them more apt to using new words and longer phrases when on their own.