Distros : Prep - Etcher: Flash!
The hard part is over, once you have Etcher installed its quite easy and safe to use to burn an ISO Image that you have downloaded onto a USB Key.
So get a USB key, make sure it's big enough and insert it into your PC, let the fun begin...

First you click on Flash from file and then you goto your image, only OS Operating System images are listed. You locate the image you want, probably in your Download folder, you did run a Checksum and gpg on it??, great, click Open to choose it.

Now for the tricky part, choosing where to burn the image to, click on Select target.

Etcher has found two drives targets
but only lists the USB key, in my case a 4GB DaneElec that is mounted on /dev/sdb, this is what I want, so I ticked its box and clicked on Select.

The other target is the laptops hard drive on /dev/sda, using dd and a simple typo error of=/dev/sda instead of of=/dev/sdb would wipe the hard drive, total disaster. Etcher hides the hard drive so preventing this happening.
Now for the final step, note you can still change the image file and target, happy with everything: click on that Flash! Button, you will be prompted for the root password, NOT A GREAT IDEA, for now put it in and click on Authenticate.(See at end of this page for a way to avoid putting in the root password).

Etcher switches to a two panel layout and the flashing starts. The left panel lists the image that is been flashed, the target and a neat progress bar. The Right Panel contains product placement, lovely.

When the flashing is completed, Etcher will verify the image.

Etcher finishes by offering you a choice to flash another image.
Having to put in the root password into Etcher every time you want to flash a USB key is not a good idea, so a work around is to run Etcher as sudo and the only password needed is your own!!! I tried the following in a terminal to see if it would work.
$ sudo /opt/balenaEtcher/balena-etcher-electron I just typed /o then tab then b then tab then b again!! [sudo] password for bryan: libva error: /usr/lib/i386-linux-gnu/dri/i965_drv_video.so init failed ready-to-show: 13.201s
And it did, there was an error but everything worked as before but did not asked for roots password when I went to flash an image.

Now how about a shortcut to that command on the desktop...Using the Mate Desktop I right clicked an empty space and choose to Create a launcher..

For the Type: I Clicked in the Drop Down menu and picked Application in Terminal
I gave it the name Etcher and bopped back to the terminal, copied that sudo command and Pasted it into the Command box. Mate picked up on the Etcher Icon.
Finally I added the comment sudo etcher and then clicked OK, the Etcher Icon appeared on the Desktop.
If you drag the Etcher icon over to the Top Bar to create a quick launch icon, the comment sudo etcher will pop up when you hover over it.

When you double click this icon on the Desktop or single click it on the Top Bar, a minimal terminal pops up looking for your sudo password, if you are setup as sudo: type in your own password and Enter.
Etcher will run as superuser and when you click on Flash from file your search for an image starts in the root directory, so you will have to drill down through /home and then your user folder. Its worth the extra hops not to be asked for the root or any other password.
So what do you think of all this preparation before you install Linux???