Digitizing cassette tapes using Windows 10 and Audition 2020

You have to bear in mind that Audition is professional software, and as such its users don't generally need to be told how to do things like this. Mainly because in principle it's incredibly simple to do, and the setup hasn't really got anything to do with Audition as such anyway, which is why you'll find no references to anything like it in the manual.

How simple? Connect the line output of your cassette player to the line input on your audio device (or on your laptop if you aren't using an external converter), select that as the input you're using in Audition, press 'record' in Audition and 'play' on the cassette recorder. When it's finished, press stop on both. Save the file. You're done. But details beyond that we can't give, because we have absolutely no idea what equipment you're using.

But that's the simple bit. If you actually want to nuance the results, there's a whole load more you need to do, and that gets more complicated. And it's not to do with Audition either - if you want some sort of an idea, read this thread: Importing Audio from cassette tape initially.