after training nlu by using rasa train nlu then what is the steps to enter there utter the responses in domain.yml for any project
Hi, welcome to the Rasa forum! 
It sounds like you might be working from an older tutorial. If you’ve installed the most recent version of rasa, you can train both the NLU and Core using the command rasa train.
To add utterances, you can open the domain.yaml file that was created in the directory you initilzed your assistant in. You can see an example of what the initial domain.yaml file looks like here. All you need to do is add a new section following the same formatting, like so:
utter_utterance_name:
- text: "your response goes here"
There’s a quick video walkthrough of building a simple assistant here that might be helpful.