Related tasks
Create a BookXRefs file based on the xrefs in an existing Frame file
Set up a more complex BookXRefs file (two groups, three xref definitions each)
Set up a shared group that is included in two other groups
Reference a common BookXRefs file
Delete specific xrefs from all files in a book
Rename specific xrefs in all files in a book
Replace specific xrefs in all files in a book
Related information
Using Special Characters

Set up a simple BookXRefs file (one group, three xref definitions)

When you run the Import XRef Definitions command with this BookXRefs file, all of the files in the book will be updated with the three xrefs, HeaderOnly, HeaderQuoted, and HeaderAndPage. If these xrefs already exist, their definitions will be updated, if they don't exist, the xrefs and definitions will be added to each file. Because there is just one group defined, you won't be prompted to select a group. 
[General] 
AltBookXRefsFile= 
DeleteXrefCode= 
RenameXRefChar= 
ReplaceXRefChar= 
EditorType=0 
 
[Groups] 
Count=1 
1=MainGroup 
 
[MainGroup] 
HeaderOnly=<$paratext> 
HeaderQuoted="<$paratext>" 
HeaderAndPage="<$paratext>" on page <$pagenum>