Installing ISAJET
First, install ypatchy on your computer. On my mac, fink install patchy works.
Then, download isajet.car , Makefile and isared.tar.gz . All are found on the ISAJET site . Put them in a folder where you want to install them, and run uncompress isared.tar.gz .
Now you need to edit the makefile with the correct paths to ypatchy and your fortran compiler. An example for a mac installation may be found here.
Lastly, run make isatools (takes time) and make to install isajet.