Run the app and you'll see:
- A top title bar
- A sidebar listing papers
- A central PDF viewer
- A right tag panel
- Click "Add Paper".
- Choose a PDF from your system.
- Choose the paper you want to delete (if necessary).
- Select a paper from the list.
- Enter a tag on the right panel and press "Add".
- You can add tags after treading the paper within the app (which is easier!).
Type a tag in the search bar to filter papers.
Sort the files by name or date modified.