Update adding-a-new-package.md (#1346)

## Checklist

- [ ] I have added
[tests](https://www.cursorless.org/docs/contributing/test-case-recorder/)
- [ ] I have updated the
[docs](https://github.com/cursorless-dev/cursorless/tree/main/docs) and
[cheatsheet](https://github.com/cursorless-dev/cursorless/tree/main/cursorless-talon/src/cheatsheet)
- [ ] I have not broken the cheatsheet

Author: pokey

docs/contributing/adding-a-new-package.md

@@ -6,14 +6,13 @@ Replace `foo` with your new package name in the instructions below.
 2. `mkdir foo && cd foo`
 3. `pnpm init`
 4. `code package.json` and update the `description` field
-5. `cd ../..`
-6. `pnpm install`
-7. `pnpm meta-updater`
+5. `pnpm install`
+6. `pnpm -w meta-updater`
 
 For any packages that you need to depend on, you can run
 
 ```bash
-pnpm -F @cursorless/foo add -D some-package
+pnpm add some-package
 ```
 
-Note that `some-package` could be a local package, eg `@cursorless/common`. In that case, you need to re-run `pnpm meta-updater` after adding the dependency, so that the Typescript references can be updated.
+from the `packages/foo` directory. Note that `some-package` could be a local package, eg `@cursorless/common`. In that case, you need to re-run `pnpm -w meta-updater` after adding the dependency, so that the Typescript references can be updated.