How Do Engineers Design Buildings?

Now right off the top I don't have any experience in structural engineering but it is the one field I want to get experience in.
Hopefully one day I can learn more about this amazing and intriguing field.
Now all I know about structural engineering is through a bunch of YouTube videos that I watch about this field.
I watch them because I want to learn more about the field. Now I understand that civil engineers use Cad-Like programs to design structures.
Some of these programs include risa 3d, etabs, and sap2000. Now I don't know how popular any of these software programs are among engineers as I heard about it on some videos and it probably varies from firm to firm.

Basically with risa 3d and all of those software engineers can design steel structures, and concrete structures and they are able to analyze the building.
So that is pretty cool and that is something I would actually want to learn how to use for fun. If I could I would probably design something tiny like a shed and try building it.
I think that would be pretty cool. Anyway, I got a lot more to learn about structural engineering and I look forward to doing so one day!