To enable ciphers properly you should be using the IISCrypto tool. Modifying the registry directly is not recommended and may not work as you expect. More importantly, if the OS doesn't support it then it won't show up anymore.
After making the change and rebooting the cipher is enabled. However when security negotiation occurs then the client and server share the supported ciphers and agree on the "most secure" one to use. Hence testing this directly isn't easy. There are online services that can tell you what ciphers are supported if you really want to test this but IISCrypto shows you that same information.