addon domain second installation of wordpress

I have a wordpress account for my website which is working fine. i recently added a second domin name to my hosting account which I also want to run wordpress. how do I install it into the second domain?

i tried transferring the original installation files to the folder for the addon domain however when I got to my second site, it does not have the setup page or login page. when i try to log in, it automatically logs me into my main first site’s wordpress back end.

is there something I am doing wrong?