Integrate okta with COBOL without gui

Hello everybody.
I’m new to okta and I have an interesting challenge.
I need to validate users with a token to access a cobol application that does not have a graphical user interface and does not access the internet. It runs on a linux vt100 terminal with character interface.
My costumer wants to use the okta verify app on his cell phone.
Well, to achieve this goal, I think of using a java jar to access the OKTA rest
apis to validate the users and release the access to the COBOL in case of success.

I took some apis and installed it in postman.
I registered some users.
I used Primary Authentication with Trusted Application and got a successful return.

But, here I am lost.
I installed okta verify on my phone but I can’t log in any of my registered users to get a token.
What do I need to do from here?
Which enroll should I use?
I would like a clearer orientation of the necessary login flow and which rest api calls I need to use and which parameters to send in them.
On the other hand I don’t understand exactly the user login flow in okta.
Can you guys please help me?
Thanks in advance.