This is the manual install which is necessary until the plugin is admitted to the store.

1. Head over to releases https://github.com/jamesmagoo/nostr-writer/releases and download a the pre-release for upcoming features. You just need 3 files: main.js, manifest.json, styles.css
2. Navigate to your plugin folder in your preferred vault: VaultFolder/.obsidian/plugins/
3. Create a new folder in the plugins folder called nostr-writer
4. Copy and paste in the 3 files that you downloaded from releases - main.js, styles.css, manifest.json i.e. into the newly created nostr-writer folder.
5. Enable the plugin by going into Settings > Community plugins > Installed plugins > toggle 'nostr-writer'.

(All of this will not be necessary once the plugin is admitted to the store.)