Hi Jan,
the hardware info is correct, no problem there.
Regarding the firmware, the file is not an executable, so to update the firmware you would need to open the file from within the Promise Utility.
Open the Utility (please make sure the utility is the correct version for Pegasus2, 4.06.0000.01)
https://www.promise.com/DownloadFile.aspx?DownloadFileUID=6740
If the Pegasus device is found by the Mac then a window will open to show the device dashboard.
Unlock the utility by clicking the lock icon in the bottom left corner.
Then, in the main Mac menu, choose Admin > Firmware Update to select the firmware file and start the process.

Kind regards,
Frank