Open the Dictionary app, go to File → Open Dictionaries Folder.
Drag and drop the “iA Markdown.dictionary” into the Dictionaries folder.
Quit and reopen the Dictionary app, go to Dictionary → Settings, scroll to find iA Markdown at the bottom of the list, and make sure it’s enabled. Then drag it up to the position you would like it to appear when looking up terms in your apps.
Open Dictionaries Folder This will open a new window, simply drag and drop your unzipped iA Markdown dictionary file there.Installed Dictionary This is how it should look. Quit and reopen the Dictionary app, then activate the dictionary in Settings.
