Irix 6.5.22 media:
https://winworldpc.com/product/irix/6522
Irix 6.5.30 media (cannot personally vouch for this, use at your own risk):
https://archive.org/details/IRIX6530TAR
Here a well-known CDROM media install guide, read this:
http://www.sgidepot.co.uk/6.5inst.html
Here is a GENERIC Network install guide:
http://www.sgidepot.co.uk/netboot.html
I would still expect you to use something like LOVE utility for doing the real network install. But reading these links will help you in understanding what the heck is going on.
A modern SCSI disk on a modern SGI should take under an hour to install a standard Irix distro...however you can add things like compilers and tools from additional CDs or files that could add extra time. Given that you're learning I would install the basic system first as as a high probability you might be reinstalling the operating system soon based a change of mind or an issue with needing to reinstall something.
Honestly if I were you be prepared to do in the installation multiple times. You're likely not going to get 100% right the first time. You also may change your mind or what you want to install and certain things are easier to install initially.
One thing that may not be well explained to you that will help in the beginning is you need to treat the SGI installation like you're installing an operating system with a ton of service packs. So you need a combination of the files from the original 6.5 OS and then all the files from the overlays (what you would consider to be a service pack). This insured that the user was still licensed for the initial OS release even as newer versions came out. The media was not released with a totally new installer make up. You always had to put some the original OS files in the installer with the service pack installer. You always boot with the first overlay CD, or the files from the first overlay if you're doing a network install. But during that install you need to feed in a bunch of CDs, or folders on a share, in a specific order to layer for the original OS files and their entitlements, then the updates to those entitlements. If you get the order wrong you'll see an enormous number of conflicts. Please note there is never zero conflicts. Most of the time you have to disable some Java client and potentially something else to get the conflict totally resolved. But if you come across an enormous number it's a sign that you put the discs in in the wrong order.
Read through the installer guide to understand what I mean but the installer was always designed for CD media. If you use a network install, unless someone has written a script for you, you're expected to feed it chunks of files manually that would've been the contents of each CD. Normally people just make a single folder for each CD, and then open each folder in the proper order as if you were inserting those CDs manually on a local media install. So the network install doesn't behave any real differently when it comes to the way files are organized. You cannot dump all the files in one folder because there are naming conflicts and you'll wind up overwriting things.
The basic steps are you first need to provision the hard disk with an SGI disk label, this is what you would think of as a partition table. You need to use the root style label which is designed to be the bootable volume. The option label is designed to be secondary storage discs and not used to boot the operating system. You'll use a program that you have to launch by hand called FX. You'll need to write an entire line to fetch it from the network if you're doing a network install. Once you have that done, though they'll be no file system formatting at this time just a partition table. You will then proceed to the install OS phase by clicking/selecting the option to install from the PROM menu. If you set up your network variables correctly that will automatically go to the server and fetch the appropriate startup file using TFTP. After that it will launch the installer that is totally command line driven with a simple menu. You will then go through the menu and can open multiple shares or folders containing the bits of the operating system installation media. Once you have all the media opened, you then tell it to go. Go means to install and it will attempt to do everything and reboot.
if you don't have any graphics card installed in the system there is absolutely no need for you to do a full Irix installation, you might want to do a minimal one as you have absolutely no graphical front end and you'll be stuck at the terminal. Unless you intend to use X11 forwarding to another system. If you do want to do things like that go ahead and do a full Irix operating system install.
Please read through the links above and then if you have any questions come back.