Change existing file in Node.js on web app to be read only

I have an existing Node.js file in my web app that needs to be changed to be read only. I need to make it readable to all users, and there are modifications that need to be made to the existing file. I’m looking for a qualified freelancer to help get this project done quickly, correctly, and with top notch security standards in place. Please let me know if you have any questions or special recommendations to make this project successful. Thank you.