1. Extract the files from the .zip file.
2. Copy the extracted files to the Igor Procedure folder. Under Windows, this folder is usually located under:
C:\Program Files\Wavemetrics\Igor Pro Folder\Igor Procedures\
If you are running Igor PRO on GNU/Linux via Wine, it is probably under:
.wine/drive_c/Program Files/Wavemetrics/Igor Pro Folder/Igor Procedures/
3. Go to the Igor Pro Folder\More Extensions\Utilities folder. Create a shortcut for the file GetInputState.xop and move it to the folder Igor Pro Folder\Igor Extensions\. This will enable SpAcAn to get inputs from the keyboard.
4. Launch Igor. The SpAcAn drop-down menu should appear on Igor's toolbar.