How can i upload images directly from controller using Activestorage in Rails 5.2?

Hello guys. For learning purposes i am developing a MangaReader using Rails. Now i would like to be able to upload multiple chapters at once, so from a given route say "Downloads/chapters", and with the guarantee that the chapters will be named in a specific format.
I would like to run a method that for each folder in that route creates a chapter and upload all the images it contains. Now i now how to create the chapter and get the name and chapter number... from the file name, but using ActiveStorage i don't now how to manually upload all the images.

Any thoughts?