Hey mate, I can see how that's unclear. You need to open the Windows Terminal or Power Shell in the downloaded folder, then you can paste the command.
So if you are on Windows, press the Windows logo key to open the menu and then type Terminal, open it. Now you have to navigate to the folder where you downloaded and extracted the repo.
Run the command
cd Downloads\botpress-inbox\botpress-inbox-main
to open the folder that has the package.json file
No you can run
npm install && npm run start
to open the app!
Let me know if that helps!