All the information about Downward Compatibility can be found in the online documentation. Search for "Running the Downward Compatibility Batch"

Here's the basic steps to run the program from CATIA:

1. Tools + Utility
2. double-click the Downward Compatibility program
3. choose the Release level to convert to
4. click the folder icon in the Document Selection section
a. click the Member option to choose the CATPart file to be converted
b. choose your Rename option
c. click the Change Target Directory option to specify where to save the converted CATPart file
d. click OK
5. click Run to run the program