WebReel

In short, at the core of the process is the Business Model Canvas (first doc in Reel). This is a layout of your Business on one page. It allows you to create hypotheses (potential business moves, product offerings, new customers, so on), test them, and then adjust the Canvas as needed. You start with the Canvas and always come back to here after every iteration to adjust and adapt.
The next document is the Agile Customer Discovery Loop. It is the big picture loop to follow to find and exploit new customers.
The rest are individual documents used to really learn about the customer and their goals. I give a summary under each one.
One important note- When doing interviews, it is important to try to get the absolute decision maker in on the actual interviews (if possible). Leaders need to see first hand what customers are saying or they won't believe it/ be as likely to fix it.

We would start by filling out the canvas to the best of our ability. Based on things you already know from your experience as an organization. Some of it would be a guess, but it is just a starting point. We would then go start-interviewing customers based on the hypotheses in the Canvas. We find out if our ideas are good/bad and you adjust until we have a great product-market fit.
Simultaneously, we are gathering any other public data that currently exists and make sure it matches what we are trying to do. This becomes a never-ending process that will allow us to Build, Measure, and Learn while staying agile and lean.
There is a lot more to this process, but this is a great starting point. I have a lot of videos and how-tos that coincide with all of this, so if you need more just let me know.