Your child requests, comments, rejects, etc. and points to the item that they want. You model the correct word and your child repeats it.
While playing with your child, you are able to label toys, items, and activities. Your child will attempt to repeat the words that you are saying. This can be an approximation, which means that they are attempting to say part of the word. For example, if you say "ball", your child may repeat, "ba".
When your child repeats after you, reinforce by repeating their attempts. You can also reinforce by saying, "I hear that would want to go outside".