I am trying to download a shell script in FreeBSD 12 in both XFCE and KDE
GUI. When I click file_installer.sh I get a window entitled "Opening file_installer.sh" that I can open or save. When I open it I get a window
called Mousepad which shows three circles to hi-lite and says "Please select an encoding below". Default(UTF-8) is not hi-lited; System(UTF-8) is hi-lited; Other is not hilited but has a number of codes from which to select. But I do not know which code to select. Below the three choices is a statement: "! Invalid byte sequence in conversion input". If Save is selected and the file is dragged to the desktop and, after making the file Executable, an application to execute the file is needed. But I do not know what application is needed. The file on the desktop is a lengthy text file (a shebang file).

When running XFCE in Xubuntu it takes me through the file_installer.sh Wizard and then an application window opens asking for an application to be written in. Again I do not know what application is to be entered.

Probably, if it's a "shell script," it needs to be run in the terminal, not from within a file manager...but I'm just guessing.

What's on the shebang line?

if you are trying to dowwnload a text file. right click on it and select save link as, then save it.

I have a Dell desktop with Ubuntu 14.04 LTS. I downloaded 14.04 years ago and I downloaded file_in-
staller.sh on the web browser and have been using it for 5 years. My box has only has 3 Gb of ram and
the LTS support runs out this year. Therefore I bought a new box with 16 Gb of ram and this is where
I can't get the .sh file loaded. I actually had the file on Kubuntu, but when I reloaded it later on
I failed to get it back. Can I transfer my OS from the old box to the new one or maybe the directory?
I use this ap 6.5 hours a day. I have tried to load this on Ubuntu 18, Kubuntu 18, Debian, and
FreeBSD 12 to no avail.

Looks like the file_installer.sh should be executable.
In a filemanager, try to open a property window on it (probably right-click) and set the x bits.
Or in the shell, run the command