First check if the original package is maintained and open to adding types. Check if the package is being actively maintained; if so, create an issue (or look for existing/closed issues) asking for types to be added, and if the maintainers would be open to merging a PR for it.
If the original package can't have the types, they should be added to Definitely Typed. Check in the DT issues/PRs if anyone else is already working on this.
If no one else is working on it, we're good to create a PR adding them: