Style Guides often have unique rules on to fomat. Check out these links to make sure you are making appropriate changes.
Note that what you see in the library display window, is NOT what you will see in the final display for any output style. Make sure you look at the preview window to determine the final format.
If you still want to change the capitalization, it is best to do it by modifying an output style.
[Follow instructions below]
Leave titles As entered: No changes are made.
Headline style capitalization: The first letter of every significant word is capitalized. Articles and prepositions are not capitalized.
Sentence style capitalization: Only the first letter of every title is capitalized.
Determine if the capitalization you want is selected (by default) for the output style of choice:
4.Highlight the Style you wish to edit and select edit:
5. On the left side of the screen look for Bibliography, and the subheading Title Capitalization and determine what the default format is [the default is the bulleted item] If you don't like it you can change it, BUT BE CAREFUL, this becomes a permanent change. A better alternative is to make a copy of the format and then make any changes to it you wish.
6. Both the Footnotes and Bibliography sections have a Title Capitalization panel. This lets you enter one style of capitalization for the titles in your bibliographic references, and another format for when the references appear in footnotes.
You can make the changes the same way you do for X5 [see instructions in box above].
Additionally, under Tools [on the main menu-bar] use the "Change/Copy/Move Fields" command to change case.