run installer.php

Trying to run installer.php from within the file I migrated to. It is Cpanel and I cannot seem to figure out how to run the installer.php from within the folder. The videos and info I have seen say to access the file from the browser window. But I’m not sure how to type in the path in the browser window to access the file on the server. I just get a 404 error on the file path I typed into the browser. What’s the trick here??? Please.