How should I request user input on mod startup

[MrFunny]

I'm trying to make mod with license and I want to authorize ppl with discord. So algorithm is like this.
User launches mc
Mod checks for cached JWT token
If not found or it expired, mod asks to enter password, if password is entered, then request to server will be sent with this password (this part ik how to do)
So basically question is how to ask user input (with ctrl+v) on mod startup and buttons like close mc and proceed. If server respond with 403 screen just refreshes and doesn't allow to proceed