good, I am new and would like to know how to execute the file that I download from here?
Pasti (STX) is one of the preservation formats which doesn't work on a real Atari ST hardware, ie. it includes a full copy protection like an original retail disks back in the day.
If you use STeem or Hatari emulator, you need to copy a file called PASTI.DLL to the same directory where your emulator executable is.
You can download the Pasti file from http://pasti.fxatari.com/
Remember to activate the Pasti option from emulator's disk manager settings :)