Deployment of LLM

Hello, I have fine-tuned an LLM with my customised dataset and deployed the same to Google Cloud Vertex AI End point.
I have also developed a mobile application to chat with the LLM. To test the application I have used base model from Hugging Face using API.
I have attached the screenshot of the same.
Now, how can I chat with the model I have deployed in Google cloud. What changed should I make to the code?
Also, how to create API Key in Google Cloud?
I’m searching everywhere but I’m not getting the workaround anywhere.
Thanks in advance.