Update HOW_TO_CONTRIBUTE.md

HOW_TO_CONTRIBUTE.md

@@ -27,7 +27,7 @@ Please note we have a [code of conduct](/CODE_OF_CONDUCT.md), please follow it i
 ## New Version process
 
 1. Make sure that the Github Actions workflow runs without any errors.
-2. Run `python tools/generate_changelog.py xgi-org xgi [last release tag]` to get the merged pull requests with their links. Paste this into the changelog file under a new heading and edit to make more legible. Associate a GitHub username with each pull request.
+2. Run `python tools/generate_changelog.py -m xgi-org xgi [last release tag]` to get the merged pull requests with their links. Paste this into the changelog file under a new heading and edit to make more legible. Associate a GitHub username with each pull request.
 3. Increase the version number in [\_\_init\_\_.py](xgi/__init__.py.py) to the new version agreed upon by the core developers. The versioning scheme we use is [SemVer](http://semver.org/).
 4. Commit these changes.
 5. Create a new release on GitHub by selecting "Releases", then clicking "Draft a new release". Click "Choose a tag" and type "v" followed by the version number and then click "Create new tag". The release title will be this same string. Paste the contents of the CHANGELOG into the "Describe this release" field. Click "Publish release". This will trigger a GitHub action that will publish the new version on PyPI.