I think maybe you need to go brush up on some HTML and CSS tutorials as well as the Bootstrap tutorials. Many can be found around the internet, some free, some not. Udemy has some pretty good classes on it as well as tutorials can be found on w3schools and the BSS site itself a bit.
The help here is basically for using the app, not teaching how to structure a website so once you have that information more intact you'll find that BSS is much easier to work with. Good luck!
In the Overview pane on the left, drag and drop the container that has the row in it and drop it on the Body element.
Then things should seem more normal. It is a general rule for me to do things that way.
Bootstrap and Bootstrap Studio are not the same thing.
Bootstrap was developed by Twitter (https://getbootstrap.com/).
Bootstrap Studio is developed by an individual entity/company/organization etc...
Bootstrap Studio is an app designed as a Drag/Drop GUI for web developers to leverage Bootstrap to build Bootstrap semantic websites.
I think that's how you would describe it all.
I was expecting BStudio to treat every Bootstrap component as a black box, but instead it shows all the internal details. I find this very confusing. I'll take time out to work through some examples.