Revs per minute LOL
I dont know why you did not find the install instructions on IM site there are there.
If you have SSH access to your linux server and root access you can install it at root level otherwise if your have SSH access to your site you can install a non-root install
The directions to install it are here. http://www.photopost.com/howtoinstall-php.html
Server admins do not need to install it. Thats only if customers do not have SSH access and the server admins are nice enough to install it