So your bot will login as the username/token you just got from a web process that collected the token.
Well thats up to you to figure out.
There are lots and lots of possiblities/methods.
My bots tend to login to chat as a bot user as apposed to the broadcaster, so I will manually collect a bot’s token and provide the process the oAuth token to work with manually.
Generally since my bots will also need a broadcasters token to work with, my web process will collect those, shove then in a database or other storage nad use interprocess communications to tell the bot it has a new token to work with. So it will collect it.