Install that file to have a new file in the SavedSims folder without the cc and find the Sim in CAS.The file can then be found in the export folder in the user file directory.Uninstall the other Sim from installed content and delete from downloads.
You will need to delete the Sim itself but you can save it either in a savegame or as a household to keep. There is a way for only Sims spread this way.
Sometimes you do want to keep the Sim, but not the cc it came with, so what can you do to keep the Sim ? Method You will need to uninstall the Sim through your launcher or deleted from your SavedSims folder. Unfortunately some package files come inside the package file of a Sim, meaning that the only way to get rid of the download is to get rid of the Sim it came with.