Almost all plugins users install into preference plugin folder. If you have opened c4d, open preference folder (Edit/Preferences/Open Preferences folder). If you have folder "plugins" (if is not "plugins" folder in preferences, create it) in opened window, open it and paste TGS Texture Manager here and close preference folder. Then go to preferences in c4d again (Edit/Preferences/Plugins/Add folder...) and add path to "plugins" folder.
In case you have TGS Texture Manager plugin (extracted) on other place on your harddrive/SSD, you need to set path to this place. For example if you have plugin in "My plugins folder" on D drive, you need to add path (Edit /Preferences/Plugins/Add folder...) to folder "My plugins folder" on D drive
Be sure you have just one installation of plugin. (You can have plugins installed on different places on drives, but with added path/folder c4d always know where to search them. But multiple instancies of the same plugin cause problems...)