Some help getting started with tidytext

Hi! I have a project I'm working on in tidytext, which I'm pretty new to. My input data is currently in the form of individual .txt files in a folder. I successfully used get_sentiments() to track the positive/negative sentiments of my data, but I'm looking to do some more advanced topic modelling.

I'm trying to work off of this guide, but I'm struggling to get started. It looks like the input data you need to do topic modelling is a DocumentTermMatrix, which I'm unsure how to create. Is there a way to turn the data I currently have as individual files into this format so that I can use the methods described in that guide?

It's discussed in chapter 5