Bot setup - Podlesnyy/YnabBot GitHub Wiki
- Add the bot by link https://t.me/ynab_with_bot

- Run /auth command

- Now you have to Authorize Telegram bot for YNAB
- After authorize you will be redirected back to the bot
- Press button Start
- Select budget for adding transactions

- Select account for adding transactions

That's all.
Now you can send message to the bot and it will add transaction info directly to your YNAB account.