There is no specific rule of where to put the Rights Retention Statement. You can: (1) add it in the first page of the article; (2) add it in the acknowledgment section; (3) add it in the message to the editor accompanying your article (cover letter). Keep the statement from the initial submission up to the final version. Keep a copy of the succsessive versions of your manuscript that have the licence notice, and achive any discusssion with the publisher to ensure you can prove you retained your rights during the whole process. Go the extra step: (1) add the text "CC BY 4.0" or "Distributed under a Creative Commons Attribution 4.0 International Licence"; and (2) add the CC BY logo to your manuscript on all versions, from submission to the final peer-reviewed version. Recommendations based on "Implementing the rights retention strategy to scientific publications - Guide to researchers" from the French Ministy of Higher Education and Research (2022)