RULE XIX OF THE STANDING RULES OF THE UNITED STATES SENATE, PART VIII, PROVIDES FOR THE FOLLOWING:
“Former Presidents of the United States shall be entitled to address the Senate upon appropriate notice to the Presiding Officer who shall thereupon make the necessary arrangements.”
My guess is you did not know this. But I do, and have since it was adopted by the Senate. And I have been mystified as to why no former president has ever asked for the privilege to address the Senate, and in turn, the People of the United States.