You probably found this page thanks to CV Toolbox warning you that you had manually installed a plugin. CV-Toolbox has no way of knowing where plugins are installed - only that they are loaded. So if CV-Toolbox tries to install the same plugin, there's a chance you'll end up with two versions of the same plugin fighting for Cinema 4D's attention. This can lead to all sorts of negative consequences. For that reason, it's best to remove the "manually installed" plugin before using Toolbox to install.

Removing Plugins from the User Preferences Folder

1. Open Cinema 4D.
2. Edit > Preferences
3. Click on the "Open Preferences Folder" button (Alternately, if you already have CV Toolbox open, go to CV Toolbox > File > Open Prefs Folder)
4. Close Cinema 4D
5. Open the plugins folder
6. Move the folder containing the plugin you want to uninstall to your desktop (as a temporary backup in case it's the wrong folder). a. If you're having difficulty finding the plugin, there's a chance it's in a subdirectory. Use your OS's search feature to find the installation. b. If you still can't find a folder that seems like a good candidate, it's probably located in your application plugin directory.
7. Re-open Cinema 4D
8. Look to see if the plugin you were looking to remove is still installed, if not, you can delete the folder from the desktop.
9. If it's still installed, you removed the wrong folder. Drag the folder from your desktop back into your plugins folder and repeat steps 5-9

Removing Plugins from the System Plugins Folder

1. Close Cinema 4D
2. Open your OS file browser.
3. Navigate to your Cinema 4D installation. a. For Windows users it will be something like C:\Program Files\MAXON\Cinema 4D\ b. For Mac user it will be something like Applications\MAXON\Cinema 4D\
4. Open the plugins folder
5. Move the folder containing the plugin you want to uninstall to your desktop (as a temporary backup in case it's the wrong folder). a. If you're having difficulty finding the plugin, there's a chance it's in a subdirectory. Use your OS's search feature to find the installation. b. If you still can't find a fold that seems like a good candidate, it's probably located in your application plugin directory.
6. Re-open Cinema 4D
7. Look to see if the plugin you were looking to remove is still installed, if not, you can delete the folder from the desktop.
8. If it's still installed, you removed the wrong folder. Drag the folder from your desktop back into your plugins folder and repeat steps 4-7