When I subscribed to the creative cloud I uninstalled my standalone Lightroom 5, and then installed from the creative cloud application manager. Some people say that it isn't necessary. It possibly isn't. If Lightroom 5 is working satisfactorily now, it's your decision. When Lightroom 6 is eventually released you will want to install that from that creative cloud application manager. You didn't provide a lot of information in your question. I assume you are aware that you must subscribe to the creative cloud in order to receive the benefits.