Hey Mike,
I try to explain it to you in a few screenshots.
First you need to get the scripts:
Go to https://github.com/darktable-org/lua-scripts and download the .zip folder.
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Open the finder an go to the Folder “~/.config/darktable” 
  
  
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unzip the .zip and copy the content to the the folder “lua”. The Path should be: /.config/darktable/lua 
 If there is no folder called lua then create one.
 It should look like this:
  
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You just need to create the luarc file. Use the texteditor to do so. 
 In the luarc you need to require the script you want to use.
  
  
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Right click on the luarc and open the information about the file. 
 You need to remove the .rtf the close the information tab and confirm that you don´t need the suffix .rtf.
  
  
The next time you start darktable the script should also start.
If you want more scripts just add a new line the same way as the other.
David
