Why do the rabbis think that only jewish people can relate to the Divine name of Tetragrammaton? If gentiles couldn’t relate the Divine name of the Tetragrammaton How can we actually believe in one God?

The belief in one G-d is certainly a commandment for every person. It is included in the Seven Laws of Noah. Regarding your question "Why do the rabbis think that only Jewish people can relate to the Divine name of Tetragrammaton", Please clarify what is this statement based on? If you give me the source of this statement I will be glad to address and clarify it.