Koma
Save the chapter you already have open. Koma reads that tab when you click the icon, then puts the reading pages in a Drive folder. Finish any “are you a person?” check on the page first.
Sign in
Sign in with the Google account you use on readerkoma.com.
Google Drive
Connect the same Google account you use on readerkoma.com. Koma only asks for the folder this extension creates.
Folder
The Koma library lists EPUBs in the folder named Koma inbox. You can point the extension at another folder, then paste that same link on the library page.