You can use the ® symbol to inform others about your trademark registration and the legal rights associated with it. Although you are not obliged to use the ®, it is a good idea to do so as it will inform competitors of your rights and It will make them think twice before using it without your consent.
Be aware that using the ® in combination with a non-registered trademark, isn’t enough to legally protect your name or logo. Only a trademark registration will give you rights to your name or logo.
There’s only one way to know if a brand is legally protected: the trademark register. If it is not listed, it means the name/logo is NOT protected as a trademark.
Sometimes you’ll see ‘TM’ mentioned. TM can be used to inform others that the specific symbol is used as an identifier of goods, but isn’t registered as a trademark (yet).