From an .iso File to an Install on a Computer

This instructable is about making a bootable flash drive from a downloaded iso file,
and about using the bootable device to start an installation on a computer.

Supplies

An iso file adapted to the computer architecture.
A flash drive to be used as a bootable device.
- If the flash drive is newly purchased, its size should be sufficient.
- Otherwise, make sure its size is at least bigger than the ISO file.
  You might have to experiment to make sure that the size is sufficient.
Optional: a flash drive, or another storage device, for backing up potentially valuable files present on the hard disk used for the installation.

Step 1: Downloading the Appropriate Version of the Iso File

Credits to DIYmasters without whom I would likely have forgotten some steps.

Before downloading an operating system ISO file,
we need to know if the computer architecture uses 32 bits-integers or 64-bits integers.

If your computer currently has Windows, Microsoft provides instructions to verify the computer architecture.

If your computer has Linux, the command uname -i returns x86_32 if the computer architecture uses 32-bits integers, x86_64 if the computer architecture uses 64-bits integers.

If your computer has macOS, by clicking on the Apple icon, in the top left of the screen, then by clicking on "About this Mac", you can know the type of processor used by the computer.
By looking up the processor, you should be able to know if the computer architecture uses 32 bits-integers or 64-bits integers.

Once the information is known, you know which version of the ISO file to download, the 32-bits or the 64-bits version.

Step 2: Creating a Bootable Flash Drive With the Iso File

Let's suppose we have downloaded Zorin OS Edu iso file,
for example a Zorin OS Edu Lite iso file for its ability to be run by older computers.

Zorin OS Edu, based on Ubuntu, is notable for its software updater that is very convenient.

A flash drive can be used to create a bootable device.
The content on the flash drive will be erased. Make sure to do a backup if needed.

Ubuntu.com offers instructions about creating a bootable USB flash drive from

Step 3: Making Sure No Data Present on the Computer Hard Drive Will Be Missed

Make sure to back up on a different flash drive or another storage device
any data stored on the hard disk that would be valuable.

The installation is likely to erase all data stored.

Step 4: Look Up the Computer Model Manual to Find How to Reboot the Computer Inside the Bios/UEFI

On the computer manufacturer's website, you should be able to find the manual for the computer.

Inside the manual, you should be able to find the instructions to re-start the computer and access the Bios/UEFI.

Step 5: Re-starting the Computer in Bios/UEFI Mode and Setting the Flash Drive As First Bootable Media

Within the Bios/UEFI is a setting to set the flash drive as the first device looked for when searching for a bootable media.
Once the setting changed and the configuration saved, set the flash drive in a USB port and re-start the computer.