There is only a single tool for creating Common Works Registration (CWR) files here. With it, you can convert CSV files into simple CWR files. An Excel template is provided.
For production, using one of these complete music catalogue solutions is highly recommended.
DMP, the simpler of the two, allows import of data from the very same template, and export of CWR files. It is free, and it can be quickly deployed to a free cloud account.
That Green Thing is much more powerful commercial solution, coming with professional support.
CSV to CWR tool is still the best option for one-time conversion. Make sure you keep the CSV file, so you can use it later for importing your metadata into one of the aforementioned solutions. For the same reason, keep any CWR acknowledgement files from receiving parties.