There are references out there - but first, some understanding might be in order. The disk-related commands only come into being when you have DOS (I'm assuming DOS 3.3 here...) booted. INIT is a DOS command, and unless/until you boot that, you won't have the command available. Now, if you booted ProDOS, there is no INIT command... that was removed for space reasons. You'd need to use a ProDOS utilities disk to initialize a disk. But if you don't have any bootable disks (and so no OS at all), no such animal exists. You'll need something else in that case.
So, depending on what you _really_ need... if you have DOS or ProDOS to boot already, here's a reference to the various "levels" of commands you get in each environment:
http://www.landsnail.com/a2ref3.htm
If you don't have any (bootable) disks at all, this is what you need to do:
http://adtpro.sourceforge.net/bootstrap.html
