New Post: IPTC tags

I've been asked to add IPTC tags to images across a site which deals with licensing images of works of art, for reproduction in magazines and so on.

They would like me to populate each image with the fields:

• Creator
• Headline
• Copyright notice
• Copyright status
• Rights usage terms
  

However, not all these options appear to be available to me under the IptcTag enum.

According to this website:
http://www.photometadata.org/meta-resources-field-guide-to-metadata

I think I can alternatively use "Byline" for the creator field.... please correct me if I'm wrong.... and I have no idea where I should place the Rights Usage Terms data.

Should I use a different field, or one of the custom fields?

This is my first time looking into IPTC tags, so if there's any basic info you think I should know, please tell me!