Copy the installer to the home folder of your user.
Looks like that would be /home/luke
Yeah, wget gives that forbidden error.
I am not a Windows user but on Linux I download the installer file to my PC then move it to the server machine using SCP.
Just a note that from your screenshots you seem to have selected to install the minimal version option of Ubuntu server from the install menu. This might be why the ls command is not returning anything.
You may be best to rerun the Ubuntu server install and just let the the standard server install.
Bob