Windows doesn't find "win_bison.exe"

[Theo]

I have followed this tutorial for using flex and Bison with VS2019 but I am stucked at an error while VS builds the project (step 5). It seems it can't find this file but I have not moved it from its original path.
Here is how it is organized :

Project_name

Debug
Project_name
Release
Project_name.sln

win_flex_bison-2.5.23

win_flex.exe
...Other files including the directory for the custom_building rules

As I said I have not modified the structure of the "win_flex_bison-2.5.23" folder.
What have I done wrong?

Thanks for your help!

[Alex Zhondin]

To use win_flex.exe or win_bison.exe (no matter from VS 2019 or standalone) you should add path to executables to PATH env variable.