Editora 0.20.0. Archived, so links from that release keep working. Read the 0.24.0 page →
Plugins: Install from File…
plugins.installFromDisk Install a plugin from a local .zip file.
How to run it
Open the command palette (M-x in the Emacs keymap) and search for Plugins: Install from File…, then press Enter. It has no default keybinding, but you can bind one in Settings → Keymaps.