The file targets/vacuum/vacuum.simics (the one you specified as an argument when starting Simics in the previous section) is a Simics script; it contains the same sort of commands that you enter on the Simics command line.
To avoid having to enter the same commands again and again when you restart Simics, open the file in your editor and add the necessary commands from the previous section (i.e., creating the device object, and mapping it into the physical memory) to the end of the script. Now, each time you start from the vacuum.simics script, your device will be automatically loaded and ready to test.