To install the macro inside of fusion, download the .setting file. Copy the settings file to the macro directory on your computer and restart Davinci Resolve. After resolve is restarted, open a fusion composition. You can either open the effects panel and click tools->macros or enter CTRL+SPACE and search for ShapeShifter.
PC: \Users\%username%\AppData\Roaming\Blackmagic Design\DaVinci Resolve\Support\Fusion\Macros
MAC: /Users/YOUR-NAME/Library/Application Support/Blackmagic Design/DaVinci Resolve/Support/Fusion/Macros