Windows
Step 1: Press Win + R to open the Run dialog.
Step 2: Paste the following path:
%AppData%\Blackmagic Design\DaVinci Resolve\Support\Fusion\Macros
Step 3: Press Enter and paste your downloaded Macro files (.setting) in this folder.
Mac
On Mac there's no %AppData%, but there's an equivalent trick:
Step 1: Open Finder.
Step 2: Press Cmd + Shift + G (this is the Mac equivalent of Win+R).
Step 3: Paste this path:
~/Library/Application Support/Blackmagic Design/DaVinci Resolve/Fusion/Macros
Step 4: Press Enter/Go and place your Macro files here.
Linux
Step 1: Open your File Manager.
Step 2: Press Ctrl + L to type a path directly (similar to Win+R).
Step 3: Paste the path:
/home/[your_username]/.local/share/DaVinciResolve/Fusion/Macros
Or using the ~ shortcut:
~/.local/share/DaVinciResolve/Fusion/Macros
Step 4: Hit Enter and place your Macro files here.