How to install 18.04 LTS 64

[Geoffrey Combes]

In the past I have upgraded using a DVD purchased from ubuntu.au 
over-writing the existing main HDD. Now I want to do something different 
and I am having great difficulty. I wish to install 18.04 on to a new 
and blank SSD such that it is the root file system replacing the old 
16.04. This time I bought 18.10 from ubuntu.au as a flash memory stick. 
Unfortunately it doesn't show up on the bios boot menu, the only bios 
system window that I can raise. Not a good start! It is not made easy by 
not being able get into the bios system as one should.

I tried a different route by downloading the iso. After partitioning the 
blank SSD using gparted I dd it with the iso successfully. But, as I've 
learn't in the past that doesn't make the image bootable. Ubuntu 
instructions lose their way after the step of downloading the iso, 
saying "it's the hard part". I have successfully installed an Armbian 
image (based on Ubuntu16.04) on an Orange Pi One board. It booted but 
only because the image was designed to do so specifically for the Orange 
Pi. I ask: Why can't I do the same with the 18.04 iso?

My other problem is that I want the new SSD to be be the root file 
system and replace the existing 16.04 root file system. I don't know how 
to do that. Surely there is a way to install an OS on to a pc which has 
only a blank main drive ( which may, or may not, be partitioned). This 
is done every day by the maker's of brand new PCs.

Your advice would be appreciated. Please don't send me to a forum site; 
they can be useful but I find them mostly chit-chat columns.

Thanks, Geoffrey Combes