0. Setup Python  ex. into C:\Python310 with PATH settled (select this flag via installation process)

1.Setup tgeraser

>pip install tgeraser

2. Create credentials.yml file, ex:

api_credentials:
  api_id: 123456
  api_hash: xxxxxxxxxxxxxxxxxxxxxxx

sessions:
  - session_name: John
    user_phone: +xxxxxxxxxxx

the hash and id got from: https://my.telegram.org/auth?to=apps

3. run and follow instructions (instead C:\PRJ\TELEGRAM\eraser\credentials.yml put yours path for credentials.yml file):
>tgeraser -i "C:\PRJ\TELEGRAM\eraser\credentials.yml"

One alternative way is: 
https://github.com/gurland/telegram-delete-all-messages