You can help improve PSOPT in a number of ways
Sending bug reports. PSOPT's issue tracking system on GitHub can be found at this link: https://github.com/PSOPT/psopt/issues/
Sending corrections to the documentation.
Discussing with the author ways to improve the computational aspects or capabilities of the software.
Sending to the author proposed modifications to the source code, for consideration to be included in a future release of PSOPT.
Sending source code with new examples which may be included (with due acknowledgement) in future releases of PSOPT.
If you have had a good experience with PSOPT, tell your students or colleagues about it.
Quoting the use of PSOPT in your scientific publications.