See guide at https://open.win.ox.ac.uk/pages/open-science/community/Open-WIN-Community/docs/gitlab/repo-doi/

If this page is no longer available for some reason, the steps are:

1. In zenodo, log in or create an account. Go to “new upload” and add details about your material. Click the “reserve” button to get the doi which will be issued by zenodo.
2. Copy this doi into your README for your project on GitLab, or other documentation. Include this in a section entitled “How to cite this material”.
3. Make a “release” of the repository. Add a note to mark this as the initial release.
4. Download the repository from GitLab (download icon on the repository home page) as a .zip or other compressed file type.
5. Upload the compressed file collection to zenodo.
6. Finalise the zenodo entry with all contributors including their ORDIC IDs. Include a link to the GitLab repository.
7. Set an embargo period for the material if it is not yet publicly available on GitLab.