In case you are not able to see Look Designer after installation, please follow the steps below.
1. Please go to Davinci Resolve preferences and check if you can see it in video plugins
If it is disabled - enable, save and restart.
If there is still a problem then:
Windows
Close DaVinci Resolve
Open OpenFX plugin cache file location
Open a File Explorer window
Go to C:\ProgramData\Blackmagic Design\Davinci Resolve\Support\
Delete the OFXPluginCache.xml file at this location
Relaunch Resolve
macOS
Close DaVinci Resolve
Open OpenFX plugin cache file location
Open a Finder window
Select Go > Go to Folder...
Type or paste in: ~/Library/Application Support/Blackmagic Design/DaVinci Resolve
Delete the OFXPluginCache.xml file at this location
Restart Davinci