Add these lines in your configuration.yaml file and change the Access Token & chat ID with yours to make it work.

Telegram Configuration for HA

# STEPS TO GET THE TELEGRAM TOKEN AND CHAT ID ARE: 
## 1. In Telegram, open a chat with @BotFather - https://t.me/BotFather and enter /newbot.     
## 2. Follow the instructions and store the token somewhere safe. 
## 3. To get a chat ID, send any message to the GetIDs bot - https://t.me/getidsbot     
## 4. Enter /start. The bot will return your chat ID  
## 5. Find your newly created bot and start a chat with it  
## 6. Add the YAML code below in configuration.yaml file in Home Assistant and restart HA


# configuration.yaml entry

# Telegram Bot
telegram_bot:
  - platform: polling
    api_key: !secret t_key
    allowed_chat_ids:
      - YOUR_CHAT_ID

# Notifier
notify:
  - platform: telegram
    name: "telegram_bot"
    chat_id: YOUR_CHAT_ID