@mmiat There is no “complete” guide because every occurrence is going to vary in some way.
Sometimes ISO’s can be directly loaded as you attempted first.
Sometimes they cannot. Which can and which can’t is not spelled out nicely.
Most bootable ISO’s will not be an installer itself.
Most installer CDs/DVDs will not be able to be directly bootable.
You have to mount iso’s and use the relative kernel and initrd files from the CD to boot.
Again, I have no clue which will work and which will not work. Nor am I about to test every possible ISO on the market to write a guide for every ISO.
In the case of booting and installing from network using the net install ISO you downloaded, you will need to mount the ISO as if it’s another disk volume. Once it’s mounted, you can direct everything to look there and which files to look for. This should work fine for debian, ubuntu, fedora, or whatever linux distro you’re attempting. For Windows, I don’t know. They often require 4GB of RAM to load into in the first place and I’ve never really attempted such a feat myself. GParted, if it’s got instructions. should work in a similar manner to Debian.
The link I gave earlier should at least provide some insight as to what needs to be loaded from the relevant disk, which is why I provided. There is no guide because it is a completely case by case situation.