Upgrading your Anet firmware, and any other Arduino based gadjet

I have it on good authority that there are now well over 1 million 3D printers worldwide, most of which use the cheap and cheerful Arduino computing board in a variety of different guises.
Most of these printers are supplied as kits which once built are ready to run on the Firmware (the operating system of the machine) that's supplied by the manufacturer, because of cost considerations it's unlikely that the Firmware will ever be upgraded and may even contain bugs that as a user you have to work around.
In this Geeky world in which we live, 100's of backroom boffins beaver away at improving the usability of this Open source Firmware, just because!
Open Source means that the code is freely available and can be used by anyone for free, and changed by anyone. At least it keeps most Hackers off the street![badass]
The upside of all this is that a Firmware system called Marlin has risen to the top of the pile and has come of age, it offers such things as:-
Power loss recovery
Linear advance (whatever that may be, it's said to improve corners of printed objects)
Auto bed leveling (enables the addition of a sensor to save having to re-level the build plate every time you start a print)
Mesh bed leveling (the Firmware measures 25 different points on the build plate and applies the correct height compensation as the axes move) (this was especially useful to me since after fitting my magnetic PEI build plate I discovered that there was a warp of up to 0.25mm over the plate)

The commonest 3 axis control board uses a chip that has 128k of permanent memory and 16k of Eeprom. The main memory contains the Firmware to run the machine and the Eeprom (Electronically Erasable Read Only Memory) which is used to carry your settings from one switch on to another.
Having used the Marlin firmware for several weeks now I really rate it. Should you decide to upgrade there are a few things you need to do first.
1/ you need a computer with a USB connection
2/ you need to know if your computer can talk to the Arduino board (sounds crazy but at least 20% of boards have been shipped without a Bootloader which is needed to talk to the Computer)
3/ get a copy of the CH340/1 USB driver, it's probably with the software that came with the printer. This driver is the only one that will work with the Arduino, you only have to run it once.
4/ using the USB cable that came with the machine, plug the machine into your computer and switch on.
5/ if you get an error (sync error is the commonest) then your board doesn't have a Bootloader. There are ways to rectify this but I personally think it's better to buy a new board, the SKR 1.4 is one of the better ones from Bigtreetech.
6/ if you don't get an error then go to 'Control panel' > 'Devices and Printers' and you should see CH340 or CH341 in the Devices page.
7/ none of the above will cause any damage to anything!

none of the above will cause any damage to anything! - - except your patience!! [badass]

One of the reasons I'm recording it is because I battled, I don't follow you tube very well and all of the 'how to's' seem to flit around the screen with their cursors assuming that everyone is as literate as they are. Even on screen instructions don't work well for me, I prefer a nice thick manual.