docs: add plugin install example

scripts/generate-plugin-inventory-doc.mjs

@@ -544,6 +544,26 @@ Source checkouts are different from npm installs: after \`pnpm install\`, bundle
 plugins load from \`extensions/<id>\` so local edits and package-local workspace
 dependencies are available.
 
+## Install a plugin
+
+Use the **Distribution** column to decide whether install is needed. Plugins that
+say \`included in OpenClaw\` are already present in the core package. Official
+external packages need one install, then a Gateway restart.
+
+For example, Discord is an official external package:
+
+\`\`\`bash
+openclaw plugins install @openclaw/discord
+openclaw gateway restart
+openclaw plugins inspect discord --runtime --json
+\`\`\`
+
+Bare package specs try ClawHub first, then npm fallback. To force a source, use
+\`clawhub:@openclaw/discord\` or \`npm:@openclaw/discord\`. After install, follow
+the plugin's setup doc, such as [Discord](/channels/discord), to add credentials
+and channel config. See [Manage plugins](/plugins/manage-plugins) for update,
+uninstall, and publishing commands.
+
 ## Core npm package
 
 ${renderTable(groups.core)}