You don't necessarily need the advanced scene switcher. That is really huge. For simple switching, the built in "automatic scene switcher" from the Tools menu is often sufficient.
In general, it works like this. In Tools->Automatic scene switcher, you create associations between Windows window titles and scenes. Then click the start button on that dialog.
As soon as the window title of any app on your PC becomes any of the defined window titles in the switcher, OBS automatically switches to the scene associated with that title. That's all. It's also possible to define a scene OBS will switch to if no title matches.
The configuration is a bit too intuitive. To create a new association, select the corresponding title from the left drop down list, then choose the intended scene from the right drop down list, then click on the big +.
You can also create partial matches. For example, if you want OBS switch to Notepad regardless of the document you might edit, you can remove the document name: change the default "filename.txt - Notepad" to "- Notepad", then press +. Now the scene switcher will switch to Notepad as soon as it is running with whatever document.