How to authenticate with the API from a console application / non web environment?

Hi,

it seems all the examples provided assumes that we are accessing the Constant Contact API from a web environment (browser). 

I am trying to create a console application in C# that will access the API. I was able to get some calls working but I had to use the API references examples (ex : https://v3.developer.constantcontact.com/api_reference/index.html#!/Contact_Lists/getLists) , open the browser console and look at the request the browser makes for the call, then copy / paste the Bearer token and use it in my app.

Since it is my understanding that the Bearer Token will only lasts 24 hours at most, obviously this wouldn't work in a real case scenario.

What are the alternatives to making this work?

Thank you!