Careful:
Install and Installer are two quite different programs.
Install (which lives in C:) is a command to make a (floppy) disk bootable.
Installer (which lives in SYS:System) is the interpreter of Installer scripts, used to install various applications.
Normally, SYS:System should simply be part of the command path. If it isn't, add the following line to your S:User-Startup:
Path SYS:System ADD
Best regards,
Niels