Stress testing is where you deliberately increase the load on a system beyond its design limit to see how it copes with high loads. The system should degrade gracefully rather than collapse.
The MHC-PMS has been designed as a client-server system with the possibility of downloading to a client. To stress test the system, you need to arrange for (a) many different clinics to try and access the system at the same time and (b) Large numbers of records to be added to the system. This may involve using a simulation system to simulate multiple users.