Install the plugin from Apps & Plugins tab in the Splice desktop app. Your plugins will automatically download to these locations unless you specify a different file path:
AU: Macintosh HD/Library/Audio/Plug-Ins/Components
VST: Macintosh HD/Library/Audio/Plug-Ins/VST
VST3: C:\Program Files\Common Files\VST3
VST2 plugins don't have a default installation location. Common locations users choose for VST2 installation:
C:\Program Files\Common Files\VST2
C:\Program Files\Common Files\Steinberg\VST2
To get the plugin up and running in Ableton Live you need to check Ableton's AU/VST settings.
Ableton Live 10
Ableton Live 11
Navigate to the plugin preferences by clicking Ableton > Preferences > File and Folder or Ableton > Preferences > Plug-Ins if you’re using Live 10 and Live > Settings > Plug-Ins
Make sure that the appropriate Plugin Sources are checked and hit Rescan. If you want to use the VST3 version of your plugin, make sure System Folders or Custom Folder is checked. If you’re a Windows user you will only have the option VST Plugin Custom Folder; click Browse, and then manually navigate to the location you installed Serum.
After you rescan your plugins, close out your DAW, and restart your device.