You will need Library Administrator access rights to make any changes to the Properties XML file. This is found in this location:
This is the 'master copy' to which Triaster software will make additions as you create approvers, authors and functions through a process library's site. You should work on a back-up copy, and replace the current copy with the updated one when you are satisfied it's ready.
Your Process Navigator (and others) will probably be configured to use the copy in 'MapStore\Stencil, Template and Properties', and you can use Process Navigator's Properties download facility to synchronise the contents of the master copy (in 'ProcessLibraries') with the PN working copy (in 'Stencil, Template and Properties' (or, indeed, elsewhere)).
In the 'Mapping Options' dialog, on the 'File Locations' tab, the field next to the 'Reload Now' button should have the path similar to this:
Clicking 'Reload Now' will update the Properties XML file specified in the 'Properties File' field with the content of the one specified in the HTTP path. It only takes one PN user to do that for it to apply to all, if a shared copy of a working Properties XML file is used.