you unzip the file to extract the .js files... choose one or all of them and copy them to src/scripts inside your pixinsight installation directory. if you want to keep them separate from the stuff that comes stock, you can create src/scripts/myAIP or whatever directory and put them in there. to be fair you can put the scripts in any directory you want, even outside of the pixinsight installation directory.
once you've put the scripts somewhere, then go to PI and select Scripts > Feature Scripts... , click "Add" and then navigate to the directory where the scripts are, and click OK. it should find the new scripts; you can check the list in the dialog box to make sure they are there (and checked.)
rob