I did answer your question. And I'll say it again here: You can select the floor as an object and click what layers appear with the object window. You can build whatever you want with the controls in the sticky notes. It was clear from your post you didn't read how the controls work, and without doing that basic bit of research there is very little anyone can do to help you.
I pointed you to the answer, and since that question gets asked by every new person that comes it, there is a sticky that answers it. As far as how to do it, it's like legos man, you stick stuff together to build whatever you want. Use whatever pieces you like to make the thing look like how you want.
If you see something specific you think is cool and you're not sure how to build it the way they did, you ask them and they will probably get you an answer in a reasonable amount of time.
Outside of sitting at your computer and doing it for you while you watch, that's literally all there is to learn.
I'm not sure if you didn't understand what I said, or will understand this, but literally anyone on the discord is happy to help, but if you don't take the time to learn the basic controls there is very little anyone can do to help you.