Trustdee you need to use botfather from telegram.
Create bot
/newbot
And then give the bot name. Name must be end with bot
/setdomain
Bot father will ask you to chose the bot. After choose , it will reply
Link your website with your bot to use the Telegram Login Widget. Widget documentation: https://core.telegram.org/widgets/login
After that , enter the domain name that you want to use.