Implement Login and Password on the E-Commerce admin module

My e-commerce website is composed of two modules - admin(for me)? and public(for everyone). There is no login name or password when accessing the admin module. I need this security function in place so that only authorized persons can access the admin module. ## Deliverables As the whole site is 'live' this project must be worked on off-line. Necessary files should be downloaded into a test server and worked on there. This project under no circumstances can impede or disrupt the flow of the current website. Changes can not? damage other working functions.