Greetings Toby,
The way to have some data fields flagged as "indexes" is pretty easy.
1 - Choose the desired data selection object and access it's properties by double clicking it.
2 - Once in, locate the "Archive/Email/fax" section and look at the options within. You should notice a "Planet Press Image options" area
3 - In those options, I am certain you can guess the steps to follow ! Click the "Index" checkbox and here you go, the field is indexed. In those options you can also give a name to that index and also place handy PDF bookmarks !
If you have any further questions about indexes or how they work, I will gladly explain it to you !
I wish you a great day !
Matt : )