Unable to install Themes

I am trying to install a dark theme. I go to the Lister Themes and it opens showing I have no themes. I click the file command but nothing happens. I have no way of installing a theme.

Do you mean the File menu does not open?

Or the menu opens but File > Import Theme doesn't open a file picker?

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I too did not perceive the File button to be an actionable button. very glad i found this thread, albeit after an hour of screwing around. maybe make it mor 'button-ish' looking or change 'File' to 'Menu' ??