You only need a GSD file if you're making the PFB-CLX into a Profibus DP slave to some other DP Master. Then you can import the GSD into a tool like COM Profibus and use it to tell the Master how to parameterise the PFB-CLX as a slave.
Otherwise, you just need SST's configuration software, free with purchase of the module.
I used one of these to scan a slave CTI module in a TI-505 rack a few weeks ago, also to scan TI-505 "Profibus RBC's" to control racks of I/O that formerly belonged to a TI-545 PLC. They're pretty clever once you get them going, but if you're not accustomed to Profibus they can be a little dense.